The utilization of sustainable cement replacement materials in concrete can control the emission of carbon dioxide and greenhouse gases in the construction industry, thus contributing significantly to the environment, society, and the global economy. Various types of sustainable concrete including geopolymer concrete are tested for their efficacy for construction in laboratories. However, the performance and longevity of sustainable concrete for civil engineering applications in corrosive environments are still debatable. This paper aims to investigate the performance of the reinforced geopolymer (GPC) and foam concretes (FC) against corrosive chloride exposure. Two long term key parameters, i.e., corrosion rate and mechanical performance of reinforcing steel in geopolymer and foam concrete were assessed to evaluate their performance against chloride attack. For experiments, reinforced GPC and FC specimens, each admixed with 3 and 5% chlorides, were kept at varying temperatures and humidity levels in the environmental chambers. The corrosion rates of the reinforced geopolymer and foam concrete specimens were also compared with control specimens after 803 days and the tensile strength of the corroded reinforcing steel was also determined. Moreover, the long term efficacy of repaired patches (810 days), in a chloride-rich surrounding environment utilizing FC and GPC, was investigated. The results suggested greater performance of FC compared to GPC under standard environmental conditions. However, the simulated patch repair with GPC showed better resistance against chloride attack compared to FC. The research also undertook the fractographical examination of the surfaces of the reinforcement exposed to 5% admixed chloride and develops models for the corrosion rates of foam concrete as a function of the corrosion rates of geopolymer concrete and chloride content. A correlation model for the corrosion rates of FC and GPC was also developed. The findings of the current research and the model developed are novel and contribute to the knowledge of long term degradation science of geopolymers and form concrete materials. Furthermore, the findings and methodology of the current research have practical significance in the construction and repair industry for determining the remaining service life for any reinforced and steel infrastructure. Large scale concreting produces emissions of greenhouse and carbon dioxide gases that impact the environment and subsequently cause socio-economic consequences ,2. The eFoam concrete (FC), which can be classified as a geopolymer foam concrete, is a recently developed lightweight structural concrete that utilizes waste material in its composition . The phyOn the other hand, fly ash- and slag-based geopolymer concretes (GPC) have been established for some time and researched extensively for their durability when incorporating various waste materials for structural and infrastructure applications ,38,39,40Therefore, there is from very limited to no research on the long-term corrosion resistance and the mechanical performance of the reinforced foam concrete in chloride-rich environments. In addition, a comparison of the corrosion resistance of foam concrete with geopolymer concrete has not been explored previously. The current research has been carried out to address this gap. Specimens of varying admixed chloride concentrations, along with control specimens of FC and GPC, were prepared and tested after 803 days of exposure for corrosion resistance and mechanical performance. In addition, the long-term efficacy of simulated patch repairs of FC and GPC with high chloride content in the surrounding concrete was investigated. Models are developed to predict the corrosion rates of FC as the function of the chloride content and the GPC corrosion rate and for the correlation between the two types of concretes.3 were prepared for foam and geopolymer concrete with 3 and 5% chlorides, respectively. The control specimens of FC and GPC with no chlorides were also prepared for comparison and kept under standard conditions of 24 °C and 50% humidity. For the preparation of the FC specimens, an electronic mixer was used in which the required quantities -contaminated concrete a, while The main objective of the current experimental program was to observe the degradation of the mechanical properties of the reinforcing steel in the GPC and FC specimen in the aggressive environments after long-term exposures. Based on the literature, it was hypothesized that the selected chloride levels, along with the temperature and humidity variation would substantiate the reduction in the tensile strength of the reinforcing steel in GPC and FC. Understanding the corrosion behavior and quantifying the reduction in tensile strength was planned to be the major outcome of the current research. Since, the tensile strength of the reinforcing steel is directly related to the service life of the reinforced concrete structure, therefore, observations of the tensile strength of reinforcing steel in GPC and FC in aggressive environments could assist for the accurate computation of the designed life of structures.The performance of the reinforced FC and GPC in a corrosive environment is measured by conducting corrosion assessment, determining the ultimate strength of the reinforcement using tensile testing and fractographical examinations. The details of the tests are as follows:2O3) and 50 g stannous chloride (SnCl2) dissolved in 1 L hydrochloric acid  by stirring for a quarter of an hour at room temperature. The corroded reinforcing bars were diped in the prepared solution for approx. one minute and then removed. These bars were then dried and further cleaned using a brush. After cleaning, the bars were weighed. The mass losses were converted to the rates of corrosion [4, W = mass loss in grams , T = time in hours, A = total surface area in cm2, and D = density = 7.6 g/cm3After 803 days, the specimens were broken open and the corroded reinforcement extracted for mass loss measurements. This involved fracturing the specimens and removing mortar from the bars. The weight of the reinforcing bar after removing the rust was recorded. This weight of the reinforcement is subtracted from the initial weight of the reinforcement prior to placement in the concrete. The difference of the two measurements is identified as the weight loss. The mass loss In grams was calculated for all the specimens after 803 days. ASTM G1-03 (2017) e1  was adoporrosion ,42,43,44The mechanical performance of the reinforced concrete under corrosive conditions was evaluated by carrying out tensile testing. The tensile tests were conducted following a mass loss measurement with a universal testing machine. The rate of loading was maintained at 1.1 mm/min according to ASTM E8/E8M-16ae1.The SEM images of the fractured areas of the corroded reinforcing steel embedded in a 5% chloride-rich environment after conducting tensile tests was performed. The purpose was to observe degradation in the microstructure of the steel due to corrosive environments after prolonged exposures.The reinforcement in the FC specimens were assessed for the extent of corrosion, The corrosion rates in FC specimens of both lower (3%) and higher (5%) chloride content showed a decline with time . The corThe corrosion rates of the FC specimens with zero chloride, 3%, and 5% Cl after 803 days of exposure are shown in The corrosion rates of steel in GPC with varying quantities of chlorides was also determined. The visual observations of the corroded bars from GPC are shown in The comparison of long-term corrosion rates of FC and GPC specimens was also performed. This comparison is shown in Furthermore, the corrosion rates of steel in the control FC were found to be slightly lower than that in GPC. This can be attributed to the compact microstructure of FC as compared to the microstructure of GPC. GPC has larger pores and voids within the microstructure of the concrete through which oxygen and moisture can easily diffuse to the embedded reinforcing steel and initiate and propagate corrosion. Hence, the initial corrosion rates of reinforcing steel in GPC are slightly higher than FC .The investigation of the repair efficacy using FC and GPC was also compared in the current research. The corrosion rates measured from the mass loss are shown in However, the corrosion rates of the end sections of the GPC specimens were found to be 0.0073 and 0.008 mm/year, slightly lower than those of FC specimen . AdditioThe performance of a reinforced concrete structure can be determined based on the mechanical properties of the reinforcing steel . ReinforThe reinforcement bars removed from the control and chloride-contaminated FC specimens showed some degradation of mechanical properties especially in the ultimate tensile strength for the highest chloride content specimens after 803 days . The ultThere was no change found in the ultimate strength of the reinforcing steel in 3% chloride FC b. There Thus, based on the stress and strain curves of reinforcing steel obtained for controlled, 3%- and 5%-contaminated chloride FC, it is inferred that the there is no significant corrosion-induced degradation of the reinforcing steel in high chloride-contaminated FC specimens after 803 days. More prolonged exposures and the higher temperatures such as 50 °C might have induced significant degradation in the mechanical properties of the reinforcing steel of FC. This can be explored along with the investigation of the porous structures of the FC as a scope of future research that can reveal the long-term performance of these concretes.The reinforcement from the GPC specimens was also tested for tensile strength. The ultimate tensile strength of the reinforcement for the 5% chloride specimen was found to be 529.6 MPa . The ultUpon comparison of the tensile strength results of the reinforcing bars from FC and GPC specimens, no major variations are observed. The reduction in the ultimate strength of the steel was slightly greater in the 5% FC a as compThe long-term durability and mechanical performance of FC against the chloride attack has not been established. The current research has shown that the corrosion rates of reinforcing steel in FC can be higher initially . HoweverThe reinforcement for the simulated repair (no chloride) of the FC specimen showed higher corrosion rates  than theThe corrosion rates of the reinforcing steel in the control and chloride-contaminated GPC specimens were found to be slightly higher than in FC. The formation of dense and compacted microstructures and the resulting refined pore structure is hypothesized as a barrier for the diffusion of oxygen and moisture to the reinforcement, subsequently, the corrosion rates decreased, even in the high chloride surrounding environment . AlternaThe patch repairs with GPC and FC concrete showed the efficacy of GPC over FC as the corrosion rates of the simulated patch repair of GPC were found to be significantly lower than those of FC . These fThe mechanical behavior of the reinforcing steel in FC and GPC with high admixed chloride content showed similar levels of degradation with time in ultimate tensile strength tests. The reinforcement in GPC was slightly more degraded than that in FC. The corrosion rates of the GPC bars were also found to be slightly higher than those of FC. This would indicate that the mechanical performance of reinforcing bars in FC is superior to those in GPC when exposed to high levels of chloride.The fractographical examination of the corroded bars was also carried out to determine the cause of the degradation in the ultimate strength of the reinforcement in 5% chloride FC and GPC specimens. The SEM images of the fractured surface of the reinforcement were taken from low to high magnifications with a spot size of 5 and WD of 10, as shown in Intergranular cracks and micro-voids have been found to degrade the mechanical properties of steel in highly aggressive environments of chloride and hydrogen ,52. The The fractography investigation confirms that it was the intergranular cracking and the formation of micro voids that led to the degradation of the ultimate strength of the reinforcing steel in the high chloride-contaminated FC and GPC specimens.2 and a low standard error estimate. Based on the data, the following model was developed:A model for the corrosion rates of reinforcement FC as the function of chlorides content and the corrosion rate of the GPC determined was developed based on the test data, with a high RThe Pearson correlation between the variables was also determined, the results are shown in 2 = 0.84 and very low standard error estimate. The developed model is as follows:A correlation model between the corrosion rates of the FCcr and GPCcr was also developed with RThe developed models will have practical significance in the field for specifying concrete. Furthermore. with the addition of more variables such as time, temperatures, and humidity, the models with applications in cold and hot environments can be developed.The corrosion rates were found to increase three-fold and four-fold for 3 and 5% admixed chloride content FC specimens as compared to the control specimen with 0% chloride after 803 days, respectively.The specimens with higher (5%) chloride contents suffered degradation of the tensile strength of their reinforcements. The tensile strengths of the reinforcements embedded in 5% chloride-contaminated FC and GPC specimen were found to be 536.2 and 529.6 MPa, respectively. The tensile strengths of reinforcement in their control specimens were found to be 552.2 and 556.21 MPa, respectively.FC showed more resilience as compared to the GPC, with respect to both the corrosion rate and mechanical behavior after 803 days. The corrosion rates of FC were found to be 5% lower than those of GPC. The degradation of reinforcement was found to be 2.89% in FC, while in GPC it was found to be 4.78% as compared to the control specimen.The fractography of the reinforcing steel indicated the presence of microcracks that induced degradation in the ultimate tensile strength. It was probably due to the chloride-enhanced hydrogen embrittlement that caused the formation of microcracks within the microstructure of the reinforcing steel in FC and GPC.2 and low standard error estimate. A correlation model for the corrosion rates between FC and GPC was also developed with R2 = 0.84.A model for the long-term corrosion rates of FC as the function of the corrosion rates of GPC and chloride content was developed with a very high RThe simulated repaired patches of reinforced FC showed slightly higher corrosion rates as compared to the GPC. The corrosion rates of the repaired section with FC were twice than those of GPC after 810 days. This was probably due to the migration of chloride, oxygen, and moisture from the surrounding chloride-rich environment to the reinforcing steel in the repaired section in FC due to its microstructure and cavities as compared to GPC.The test results suggest that the test duration could be even longer for such experiments to observe significant variation of the mechanical properties. Moreover, investigations for the porous structure and solid phases of the GPC and FC should be carried out as the scope of future research.The current paper has presented a comparative analysis of the performance of reinforced foam and geopolymer foam concrete against severe chloride attack under standard environmental conditions. Specimens with 3% and 5% chloride containing reinforcement bars were tested for the corrosion rate and tensile strength at 803 days. Their corrosion rates and mechanical behavior were compared with respective control specimens without chlorides. Simulated repaired patches of FC and GPC were also investigated for their efficacy in high chloride applications. Based on the results, the following findings and recommendations can be summarized:Finally, to conclude, the results presented in the research have practical significance. With further testing and the incorporation of more variables, very accurate models for the degradation of FC and GPC can be developed.


Forensic handwriting examinations are a critical part of the criminal justice system, seeking to determine whether handwritten documents can be attributed to specific writers by comparison to known exemplars. This paper summarizes a 5-y research study designed to assess the accuracy and reliability of forensic handwriting comparison decisions, which is important in assessing scientific validity for admissibility in court. Here we report the results of the largest-scale study yet conducted to measure the accuracy, reproducibility, and repeatability of conclusions made by practicing forensic document examiners when comparing samples selected to span a range of quality, quantity, and attributes found in casework. Forensic handwriting examination involves the comparison of writing samples by forensic document examiners (FDEs) to determine whether or not they were written by the same person. Here we report the results of a large-scale study conducted to assess the accuracy and reliability of handwriting comparison conclusions. Eighty-six practicing FDEs each conducted up to 100 handwriting comparisons, resulting in 7,196 conclusions on 180 distinct comparison sets, using a five-level conclusion scale. Erroneous “written by” conclusions  were reached in 3.1% of the nonmated comparisons, while 1.1% of the mated comparisons yielded erroneous “not written by” conclusions . False positive rates were markedly higher for nonmated samples written by twins (8.7%) compared to nontwins (2.5%). Notable associations between training and performance were observed: FDEs with less than 2 y of formal training generally had higher error rates, but they also had higher true positive and true negative rates because they tended to provide more definitive conclusions; FDEs with at least 2 y of formal training were less likely to make definitive conclusions, but those definitive conclusions they made were more likely to be correct . We did not observe any association between writing style (cursive vs. printing) and rates of errors or incorrect conclusions. This report also provides details on the repeatability and reproducibility of conclusions, and reports how conclusions are affected by the quantity of writing and the similarity of content. Strengthening Forensic Science in the United States: A Path Forward .Forensic science is under scrutiny, particularly for pattern-based disciplines in which source conclusions are reported. The National Research Council report  Forward  stated t Methods  expresse Methods . Althoug Methods –10, the This study was conducted to provide data that can be used to assess the scientific validity of handwriting comparisons, for use by policy makers, laboratory managers, the legal community, and FDEs. This study follows the approach used in the previous FBI Laboratory–Noblis latent print black box study  and late1.A forensic handwriting examination involves a side-by-side comparison of questioned and known writing samples for the purpose of determining whether the questioned writing was written by the writer of the known material. Questioned writing is a body of handwriting for which the writer is unknown. Known writing is a set of writing samples that are known to have been prepared by one specific individual. The forensic comparison of handwriting and the conclusions made are based on the training, education, and experience of the FDEs. There is, currently, no generally accepted quantitative model that can be used as the basis for source conclusion decisions by the FDEs.Ideally, a handwriting comparison involves questioned writing that is original, is freely and naturally prepared, and contains a sufficient quantity and quality of writing. Questioned writing that is limited in one or more of these attributes may provide insufficient evidence to make a source determination. A handwriting comparison should also, ideally, include known writing that is original and freely and naturally prepared; is comparable to the questioned writing in format, style, characters, and character combinations; and is provided in sufficient quantity and quality to be representative of the individual’s range of writing. Limitations in the questioned or known writing may result in inconclusive or qualified conclusions.A forensic handwriting comparison involves greater complexity than many other pattern-based forensic disciplines. Since handwriting is a learned neuromuscular activity , the FDEThe predominant method for forensic handwriting examinations is known as analysis, comparison, evaluation, and verification (ACE-V). The analysis phase involves an independent evaluation (using proper lighting and magnification) of each questioned and known writing sample to assess whether the writings are original  and freely and naturally prepared and have sufficient quantity and quality of characteristics to be deemed suitable for comparison. Next, the side-by-side comparison involves assessment of comparability between the questioned and known writing, documentation of class and individual characteristics in the questioned writing, and the determination of whether or not those characteristics are also evident in the known writing samples. The evaluation phase follows, at which time the forensic examiner assesses the quantity and weight of similarities, differences, and limitations, to decide what conclusion is warranted. Finally, the examiner's conclusion is verified by another competent examiner. This method is discussed in more detail in various forensic document working group publications –17.2.SI Appendix, Appendix A for further details.The full study protocol was approved by the FBI’s Institutional Review Board (IRB) for Human Subjects Research. This section summarizes the participants, study design, and the handwriting samples; see 2.1.Participation was open to practicing examiners who had conducted operational casework within the previous 2 y, making conclusions using a conclusion scale of at least five levels. A total of 86 US and international handwriting examiners participated in this study, with US participation principally from nonprivate federal and state entities. Of the 86 participants, 64 completed at least 90 of the assigned comparisons.Participation was solicited at relevant conferences and via professional organization announcements, email communications, and direct requests to laboratory management. No participants who met the requirements were barred from participation. Participants were required to complete an IRB-approved informed-consent form and background questionnaire prior to starting the study. The questionnaire responses were used to assess performance relative to examiner variables such as training, experience, and certification, as well as to inform an understanding of the participating examiners’ operational procedures, casework profiles, and affiliated agencies .SI Appendix, Appendix C1 for all participant background survey responses.Participants represented a broad cross-section of the FDE community. Of the 86 participants, 63% were employed by US federal, state, or local agencies, 27% were employed by international government agencies, 34% worked at private practices or companies, and 8% were academics (overlapping categories sum to over 100%); 41% conduct handwriting examination casework daily (26% a few times a week); 41% had testified in a legal setting at least 20 times (including depositions); and 73% had formal training of 2 y or more . Participants were highly experienced: 50% had at least 16 y of experience. See 2.2.Each participant was asked to perform 100 handwriting comparisons over a period of about 10 mo. The test was administered using custom web-based software that presented examiners with 300-ppi digital images of each writing sample in the comparison set and collected all responses. Note that this study focuses on conclusions by individual FDEs, and therefore does not include verification of examiner conclusions, which is part of the ACE-V methodology.•Written)The questioned sample was written by the known writer (•ProbWritten)The questioned sample was probably written by the known writer (•NoConc)No conclusion (•ProbNot)The questioned sample was probably not written by the known writer (•NotWritten)The questioned sample was not written by the known writer  and “qualified” conclusions (ProbWritten and ProbNot). In casework, these conclusions are considered “qualified” because they must be accompanied by a clear statement that they are not definitive, and limitations must be documented in reports and communicated in testimony.For some analyses we combine these responses, referring to “definitive” conclusions  2013 standard , 24% useSI Appendix, Appendix D for the instructions provided to participants.In addition to the conclusion, for each comparison, participants provided responses about sample limitations, difficulty of the comparisons, variation present in the writing, skill of the writer(s), style of writing, the two most influential attributes, and the basis of exclusion, if applicable. Participants had the option to comment on each comparison. For further detail, see 2.3.Each comparison set (QKset) included one questioned sample (Q) and up to five samples from one known writer (K). Each participant was assigned 100 QKsets: 44 mated QKsets (in which the questioned and known samples were from the same writer) and 56 nonmated QKsets (in which the questioned and known samples were from different writers). The mating and ratio of mated to nonmated sets was not known to the participants. The participants could receive no more than 10 QKsets at a time for examination. The number of mated and nonmated sets within any given packet of 10 QKsets varied. To assess intraexaminer repeatability, each participant was assigned 10 QKsets that contained repeated imagery from an earlier comparison . These repeated sets were assigned different QKset numbers and were separated from the initial comparisons by a median of 70 QKsets, to minimize the chances of participants recognizing the samples.SI Appendix, Appendix A3.2 for content). Approximately half of the QKsets were designed to contain the same text between the questioned and the known writing samples. The study design controlled the samples assigned to each participant in order to assess the effects of the quantity and the comparability of writing. Cursive, handprinted, and mixed styles of handwriting were all represented. This study did not include signature comparisons. To the best of our knowledge, the handwriting samples were prepared freely and naturally, and no instruction was given to writers to purposely distort their handwriting samples; this was stated explicitly in the instructions to participants. All results reported in this study are the result of digital image comparisons. Although an optional physical subtest was offered, it was abandoned due to lack of sufficient participation.Most questioned handwriting samples (80%) were approximately half of a page in length; the remainder were generally one-sixth of a page in length, except each participant received two QKsets in which the Q was limited to an address. Known samples ranged from one to five samples of writing from a single writer . Content was either free text or directed material such as specific addresses, the modified London letter, or the the Center of Excellence for Document Analysis and Recognition Forensic Examination (CEDAR-FOX) letter A total of 180 distinct QKsets (78 mated and 102 nonmated) were created from 230 distinct writers, selected from a pool of four sources containing more than 4,500 total writers. The handwriting samples were selected to span a range of attributes and difficulty found in casework: The study was designed to have each participant receive a distribution of samples that, collectively, could be considered to be similar to those encountered in casework. The relative difficulty of any forensic test is driven, in part, by the methods used to select nonmated subjects. In this study, we selected nonmated subjects that would appear to be similar when assessed by a layperson (“close nonmates”). This study does not include comparisons of arbitrary subjects with dissimilar styles of writing that could easily be distinguished, although some casework may include such easy comparisons. Subjects for nonmated QKsets were selected using a three-step process. First, writing samples were categorized into groups of potentially similar writers utilizing layperson evaluations. In parallel, all pairs of writers within and between multiple datasets were compared using the Forensic Language Independent Analysis System for Handwriting Identification  automated handwriting identification system: Highest-scoring nonmates were selected for follow-on manual review. Next, layperson members of the study team reviewed these resulting groups and selected proposed pairs of “close nonmates.” Finally, the FDEs on the study design team used these proposed pairs to select the final sets of nonmated QKsets; nonmated subjects the study team FDEs considered “easy” comparisons were not included in the study, so the resulting dataset focused on moderate and difficult nonmated comparisons. Some individual writing samples in nonmated QKsets were cropped to remove grossly different characteristics. , each participant who completed the study was assigned 10 QKsets twice: The responses on second assignments were not included in most analyses because a subset of the QKsets would have a disproportionate effect on the results, and because the second responses are not statistically independent. For this reason, second responses were not used to calculate overall conclusion rates.SI Appendix, Appendix E for details on the datasets and test yield).For most analyses, we use the baseline dataset , which omits the 620 second assignments. For analyses of repeatability, we use the repeatability dataset, which includes 620 pairs of first and second assignments  by 65 participants on 20 distinct QKsets. For the analyses that computed and compared rates for individual participants, we use the examiner comparison dataset, a subset of the baseline dataset that is limited to those participants who completed at least 50 QKsets each  —overall (including repeats), 31 to 81 responses were received per QKset .3.1.SI Appendix, Appendix F). Accuracy refers to the extent to which participants’ conclusions agree with known source attribution (ground truth). Accuracy cannot be described using a single number but can be measured using a variety of metrics (detailed in ProbWritten and ProbNot). The proportion of trials on mated QKsets resulting in Written conclusions  was 54.0%, but an additional 34.3% of trials resulted in ProbWritten conclusions , so a total of 88.3% of trials on mated QKsets were consistent with ground truth.NotWritten conclusions  was 29.6%, and an additional 47.8% of trials resulted in ProbNot conclusions , for a total of 77.4% of trials on nonmated QKsets that were consistent with ground truth.The use of a five-level conclusion scale requires consideration of how to address the results of qualified conclusions , and an additional 4.8% of trials resulted in incorrect ProbWritten conclusions . Thus, 7.9% of the conclusions in the nonmated trials contradict ground truth. On mated QKsets, 1.1% of trials resulted in erroneous NotWritten conclusions , and an additional 2.1% of trials resulted in incorrect ProbNot conclusions . Consequently, 3.2% of the conclusions in the mated trials contradict ground truth. NoConc responses are regarded as neither correct nor incorrect, since they cannot be assessed in terms of ground truth: The proportion of trials resulting in NoConc conclusions on mated QKsets was 8.5% and, for nonmated QKsets, was 14.7%. See SI Appendix, Appendix F2 for details regarding accuracy and error rates, and CIs.Throughout this paper, we will use the term “error” to refer to definitive conclusions that contradict ground truth and refer to nondefinitive qualified conclusions that are not consistent with ground truth as “incorrect.” The reason for this distinction is that, in practice, participants explicitly differentiate between definitive and qualified conclusions, which is intended to convey different strengths of conclusions and/or different perceived weights of evidence, and, therefore, it would be inappropriate to lump them together into a single category of error. On nonmated QKsets, 3.1% of trials resulted in erroneous NotWritten conclusions. Further discussion of the challenges associated with eliminating writers is provided in SI Appendix, Appendix F5.Note that the FNRs are lower than the FPRs, and that the TNRs are lower than the TPRs; this is unlike other pattern fields , in whiWritten responses were correct , as were 97.2% of NotWritten responses , 84.6% of ProbWritten responses, and 96.7% of ProbNot responses. These rates are notably affected by the proportions of mated vs. nonmated data; see SI Appendix, Appendix F3 for details and projections. The rates of accuracy and error were not evenly distributed by QKset or by participant, as is discussed further below.An alternative method of describing accuracy is through the use of conditional probabilities, which assess the likelihood that a given conclusion is correct. Overall, 93.1% of 3.2.Written conclusions (TPRPRES) ranges from 6 to 88%, and the combined proportion of Written and ProbWritten conclusions ranges from 32 to 100% (15 QKsets achieved 100%). On the 102 nonmated QKsets, the proportion of NotWritten conclusions (TNRPRES) ranges from 3 to 62%, and the combined proportion of NotWritten and ProbNot conclusions ranges from 23 to 98%. Note that over half of the mated QKsets (45/78) result in a majority definitive Written conclusion, but only two of the nonmated QKsets result in a majority definitive NotWritten conclusion.In terms of conclusions consistent with ground truth, on the 78 mated QKsets, the proportion of NotWritten conclusion in the baseline dataset (42 have at least one NotWritten or ProbNot conclusion). The proportion of erroneous NotWritten conclusions (FNRPRES) ranges up to 9%, and the combined proportion of erroneous/incorrect NotWritten and ProbNot conclusions ranges up to 34%. For nonmates, 55 of the 102 nonmated QKsets have at least one Written conclusion in the baseline dataset (89 have at least one Written or ProbWritten conclusion). The proportion of erroneous Written conclusions (FPRPRES) ranges up to 27%, and the combined proportion of erroneous/incorrect Written and ProbWritten conclusions ranges up to 67%.In terms of conclusions contrary to ground truth, 22 of the 78 mated QKsets have at least one NoConc responses represent a relatively small percentage of the responses: Only 6 mated and 13 nonmated QKsets received more than 25% NoConc responses. It is the majority response for two QKsets, and is the consensus response in terms of average or plurality for 11 QKsets.x axis in Bottom Right). The FPRPRES on the 10 QKsets from twins was 8.7%, compared to just 2.5% on the 92 nontwin nonmated QKsets. Of the 114 erroneous Written conclusions in the baseline dataset, 28% (32/114) were on nonmated QKsets collected from twins; 11% (13/114) occurred on the nonmated twins QKset that is shown in The 10 QKsets that included twins as nonmated subjects had disproportionately high error rates , participants assessed how the overall difficulty of the comparisons in this study corresponded to their casework: 12% indicated “easier,” 80% indicated “similar,” and 8% indicated “harder.” These assessments of overall difficulty may be debatable given that some participants made incorrect responses on comparisons they considered easy. However, if we ignore participants for whom 5% or more of responses were erroneous or incorrect yet assessed as easy, very easy, or moderate, the overall assessments are not notably different: 12% indicated “easier,” 82% indicated “similar,” and 6% indicated “harder.” Note that the results by difficulty provide insight into how data selection relates to the distribution of conclusions: If this study had included a greater proportion of easy comparisons, the conclusion distributions would be expected to shift to be more definitive, whereas, if it had included a greater proportion of difficult comparisons, the conclusion distributions would be expected to shift to be more inconclusive. See SI Appendix, Appendix M for additional details regarding participants’ assessments of difficulty.The distribution of responses is strongly associated with the perceived difficulty of the comparison. Each participant assessed the difficulty of each comparison on a scale of . Easier comparisons were associated with higher rates of definitive conclusions and lower rates of inconclusives: For example, 88% of “obvious/very easy” comparisons were definitive conclusions, and none were inconclusive; this contrasts with the “very difficult” comparisons, in which 10% were definitive and 51% were inconclusive. Assessments of easy comparisons are not proof against error: Of the 23 erroneous 3.3.Written vs. NotWritten responses  provides a method to measure the relative amount of corresponding vs. contradictory information assessed by participants for each QKset.In this study, a given response can be evaluated in terms of whether it is consistent with or contradicts ground truth, but there are no such absolute criteria to judge whether a definitive or qualified conclusion is the appropriate response for a given comparison. FDEs use their expertise to determine whether a given comparison contains sufficient information to make a definitive conclusion, as opposed to a qualified conclusion or no conclusion. In making a comparison, FDEs assess a variety of factors in determining whether the samples are sufficient to make a given conclusion . However, there are no precise criteria or thresholds that clearly delineate what constitutes sufficient information to make a specific conclusion for a given comparison. In the absence of specific criteria, we evaluate, in ProbNot), whereas, on mated data, there is a range of consensus from definitive to qualified, and the four methods all show a consensus for the definitive conclusion (Written) on nearly half of the mated QKsets. This shows an asymmetry in Written vs. NotWritten conclusions: There was often a consensus among participants for Written conclusions, but rarely for NotWritten conclusions. This result indicates the relative difficulty of excluding vs. identifying a writer in this study as the source of a sample; see SI Appendix, Appendix F5 for additional discussion.Majority consensus may arguably serve as a reasonable mechanism for determining the most appropriate conclusion  for a given comparison. For QKsets that do not have a majority, the plurality, average, and/or IQR may be a suitable proxy. Note, however, that the distinctions between these approaches can be made here because over 30 FDEs provided responses for each QKset. In casework, determining the appropriate response will necessarily be based on the conclusions of a few FDEs: There is unlikely to be a difference between majority, plurality, and average if only three FDEs review a comparison, and IQR cannot be defined for fewer than five responses.ProbWritten using both metrics . Erroneous NotWritten conclusions were made by 17 of the participants, but one participant made seven such errors, thus accounting for 22% of the total (7/32).Rates of accuracy and error were not evenly distributed among participants: in the baseline dataset, nearly half of the participants (42/86) reported at least one erroneous SI Appendix, Appendix J for tables and additional figures).Because of the use of a five-level conclusion scale, FDE performance cannot be assessed using a single measure: Performance is multidimensional and must be based on rates of errors and incorrect conclusions  and rates of correct conclusions  but must also consider the relative proportions of definitive vs. qualified conclusions and indeterminate responses. Written conclusions had an FPR of 24% and FNR of 5% (blue diamond); following that shape to the other quadrants, we see both IAR and INR for that participant were 2%. In Written conclusions in the baseline dataset .For example, in the top right quadrant of Written conclusions (both correct and erroneous), was wrong on most ProbWritten conclusions (13/17 ProbWritten were on nonmates), but made few NotWritten or ProbNot conclusions; this participant could be seen as aggressive on Written and ProbWritten conclusions but cautious on NotWritten and ProbNot conclusions.The interrelations of these rates are instructive when reviewing the three participants with the highest FPRs. The participant shown with a blue diamond rarely made qualified conclusions and could be seen as overly decisive. The participant shown with a red diamond made both definitive and qualified conclusions but was disproportionately incorrect on all types of conclusions. The participant shown with a gold diamond made many Written and erroneous NotWritten conclusions (Top Right Quadrant): Of the eight participants with the highest FPRs, five had a 0% FNR. There is an association between erroneous Written and incorrect ProbWritten conclusions (Top Left Quadrant): Most participants who had an FPR above average also had an above-average IAR; interestingly, two of the participants with the highest FPR (blue and red diamonds) had low IARs, and the participant with the highest IAR had a 0% FPR. There is not a notable association between erroneous NotWritten and incorrect ProbNot conclusions (Bottom Right Quadrant): Most of the participants with an above-average INR had a 0% FNR. There is not a notable association between incorrect ProbWritten and incorrect ProbNot conclusions (Bottom Left Quadrant).There is not a notable association between erroneous Written conclusions made few NotWritten conclusions. Participants with high TNR and high TPR often had high error rates. There are only five blue open circles, indicating participants who were above average on TNR and TPR and below average on all error rates. One participant  made only definitive conclusions, resulting in one false positive and one false negative, and all other responses were either true positives or true negatives.NoConc responses are considered neither correct nor incorrect, as they are neutral with respect to ground truth. Participants who disproportionately make NoConc responses would avoid errors , but would also avoid making correct conclusions , and would thereby be ineffective. Eight participants made NoConc responses on over 25% of trials, two of whom made NoConc responses on the majority of trials (55% and 71%).Written or NotWritten), and an additional 12 never made any NotWritten conclusions. One participant only made definitive conclusions . Nine participants never made NoConc responses. These tendencies would affect rates of accuracy and consensus. For example, the participants who never made definitive conclusions would necessarily have TPR, TNR, FPR, and FNR all equal to 0%. Consensus among examiners is necessarily limited by this—in effect, over a third of participants (25/70) did not use the full conclusion scale. See SI Appendix, Appendix J2.1 for details.Some participants avoided specific conclusions. Out of the 70 participants in the examiner comparison dataset, only 45 used every type of conclusion. Three participants never made any definitive conclusions , participants were asked a number of questions about their training. Using their responses, participants were grouped based on the 2013 SWGDOC recommendations for minimum training requirements . Accordingly, the training group A participants had lower rates of both erroneous  and correct  conclusions, but the decisions they made were more likely to be correct, resulting in higher predictive values than their training group B counterparts . Differences between the training groups were significant [compared using a χ2 analysis with Bonferroni-adjusted Pearson residual post hoc tests . The trend seen in training group B in which a larger proportion of conclusions were definitive, resulting in more correct answers but higher error rates, was also seen in Kam et al.’s . These combine the rate for a definitive conclusion  and the rate for the corresponding qualified conclusion  by weighting the qualified conclusion as half the definitive conclusion . Given there is no absolute means of assessing the relative values of definitive vs. qualified conclusions, this makes the simple assumption that costs and benefits of qualified conclusions are half those of definitive conclusions: For example, this assumes that the benefit of a correct ProbWritten conclusion is half the benefit of a correct Written conclusion, and the cost of an incorrect ProbWritten conclusion is half the cost of an erroneous Written conclusion.To further characterize the performance of FDEs in this study, we utilized a multiphasic approach for detecting and reporting any associations between participants’ background and performance. In order to assess performance in light of correctness, definitiveness, and the relative value/cost of making definitive vs. qualified conclusions, we developed four weighted performance ratios  of the background attributes exhibited sufficient support to indicate an association with any of the weighted performance ratios. Because these analyses are based on conclusion rates calculated for each participant, we limit these analyses to the 70 participants who completed at least 50 comparisons (examiner comparison dataset); the remaining 16 participants completed as few as 20 comparisons each, which would be inadequate for reliable estimates of individual rates.These four weighted measures of performance were evaluated with respect to 27 background attributes using two complementary approaches: variable importance analysis (VIA) and attribute-specific significance testing. VIA considers all attributes simultaneously and was executed by coupling linear regression and random forest analysis to yield importance scores. On the other hand, significance testing was conducted for each attribute individually using the Kruskal–Wallis test to yield x K2 and  for addiWritten and/or ProbWritten on nonmated pairs) than group B. Similarly, with regard to training provider, participants who did not have formal training and/or were self-trained had significantly higher weighted FP–IA ratios than participants trained by US state agencies, and marginally higher ratios than participants trained by US federal and US local agencies. Note that training program and training provider are highly correlated attributes, with a bias-corrected Cramer’s V  and training provider. Participants in training group A  had significantly lower weighted FP–IA ratios  and reproducibility (interexaminer consistency): Repeatability refers to the extent to which a participant provides the same conclusion when given the same QKset on different occasions, whereas reproducibility refers to the extent to which different participants agree on conclusions when given the same QKset. The lack of repeatability and reproducibility can be described as system noise, which Kahneman et al.  define aWritten vs. NotWritten). These results suggest that the majority of the occasion noise lies within participants’ inconsistent assessments of the strength of their conclusions rather than differences in their interpretations of source. Conclusions consistent with ground truth  were repeated at least 73% of the time. Participants generally did not repeat their own NoConc responses, suggesting that these assessments are less stable than the other conclusions. Of the 47 participants who each completed 10 repeated QKsets, only one participant repeated every conclusion exactly.In this study, each participant who completed the study was assigned 10 QKsets on two different occasions (separated by a median of 70 QKsets). These repeats resulted in 620 pairs of conclusions by 65 participants on 20 distinct QKsets (repeatability dataset). Overall, 68% of conclusions were repeated exactly, and 92% were repeated within ±1 conclusion category; only 1% of conclusions were diametrically opposed  were made on the first assignments of repeated QKsets, of which 8 (40%) were repeated on the second assignments, and another 3 (15%) were changed to ProbWritten. Overall, there were a total of 121 FPs on 55 distinct QKsets: 84 on assignments that were not repeated and, within the repeatability dataset, 20 FPs on first assignments and 17 on second assignments; there were 8 FPs repeated . Three of the repeated FPs were made by the participant with the highest rate of erroneous Written conclusions (shown as a blue diamond in Written conclusions by 18 distinct participants: 13 on first assignments (Baseline Dataset) and an additional 10 on second assignments. See SI Appendix, Appendix H for more detailed repeatability results.Most errors and incorrect responses were not repeated. On mated QKsets, no erroneous Written on a mated QKset, 60% of the other participants also responded Written, 33% responded ProbWritten, and 5% responded NoConc. The reproducibility of responses is much lower than the repeatability of responses. One may expect that knowing an expert’s conclusion would be a good basis to predict the conclusions of other experts, but the only instance in which a majority of participants reproduced conclusions exactly was for Written conclusions on mated data. Overall, 40.4% of conclusions are reproduced exactly , and 84.5% are reproduced within ±1 conclusion. However, only 1.2% of conclusions resulted in contradictory conclusions, with one examiner reporting Written and a second examiner reporting NotWritten . Similar to the occasion noise observed for repeated responses, much of the variability between different examiners’ responses can be attributed to disagreements regarding the strength of conclusions (within ±1 conclusion) rather than disagreements regarding interpretations of source. In the reproducibility results, the distributions of responses are remarkably similar regardless of conclusion type: Particularly for nonmated data, knowing one participant’s response is a very weak predictor of other participants’ responses. Repeatability and reproducibility are both associated with training groups, in that training group B has a greater proportion of conclusions that differ by three or four categories, which could be expected from the higher error rates and increased proportions of definitive conclusions. There is no notable effect on reproducibility if limited to the participants who reported all conclusions . High levels of reproducibility are generally desirable, but are problematic if errors are reproduced. For erroneous Written conclusions, 7.9% were reproduced exactly, and an additional 11.7% resulted in the second examiner reporting ProbWritten. For erroneous NotWritten conclusions, 2.2% were reproduced exactly, and an additional 5.7% resulted in the second examiner reporting ProbNot. See SI Appendix, Appendix I for more detailed reproducibility results.We evaluated the reproducibility of responses based on all pair-wise combinations of responses from different participants on the same QKsets . For example, for every participant who responded Written on the first assignment of a mated QKset, on the second assignment of that QKset, that participant responded Written 83% of the time, or ProbWritten 17% of the time. In terms of reproducibility (in the bottom row of the mated reproducibility chart), for every participant who responded Written on a mated QKset, 60% of the other participants also responded Written, 33% responded ProbWritten, and 5% responded NoConc. In comparing the repeatability and reproducibility results, note that the reproducibility distributions of responses are remarkably similar regardless of conclusion type: Particularly for nonmated data, the categories are close to vertical rather than the diagonals seen in the repeatability results.3.7.To evaluate the effect of sample-related factors on accuracy, this study conducted a methodical analysis of the effects of three factors: quantity of questioned writing, quantity of known writing, and content comparability. The quantity of the questioned writing was divided into three categories: long , short , and address (QA). The quantity of known writing was limited to one, three, or five pages of known writing . Content comparability was divided into same  and different . To conduct the analysis of the effects of quantity and comparability of writing, 32 pairs of QKsets were created, with each pair varying a single factor but otherwise keeping all factors consistent. For example, a factor analysis evaluating the effect of content comparability presented a short questioned sample and three pages of known writing with either the same or different content as the questioned writing (QS-K3-x). Two QKsets were created that contained the same questioned sample, but one QKset contained content in the known writing that was identical to the questioned (QS-K3-S), whereas the other QKset contained known writing content that was different from the questioned (QS-K3-D). Each participant was assigned one QKset from each of the 32 pairs, so that the effect of each factor could be assessed by comparing half of the participants with the other half.Written or ProbWritten conclusions and a significant decrease in NoConc conclusions—on mated QKsets that contained a long questioned sample and different content between Q and K (QL-Kx-D). When participants were presented with the same vs. different content, there was a significant increase in correct Written conclusions, a significant decrease in NoConc conclusions, and a significant decrease in erroneous NotWritten and incorrect ProbNot conclusions—on mated QKsets that contained a short questioned sample and three pages of known writing (QS-K3-x). Both of these results show that more known samples and adequate comparability to the questioned writing samples increase the probability of accurate conclusions. In practice, FDEs can often request additional known writing samples (or request known samples that are directly comparable to the questioned samples), but, in this study, they were restricted to the samples provided. Overall, significant differences in accuracy were not detected for the majority of the factor pairings, but there were trends observed for a number of factors that were not statistically significant due (possibly) to the limited sample size.Two of the factor evaluations exhibited significant effects: On mated comparisons, increasing the quantity of known writing or going from different to the same content resulted in a significant increase in correct conclusions. When participants were presented with more known samples (K5 vs. K1), there was a significant increase in correct Written conclusions and a notable decrease in NoConc conclusions; this result persisted even when the questioned writing was extremely limited and contained only an address. This same effect was observed for nonmated comparisons, but only when the QKset contained extremely limited questioned writing: There was an increase in correct NotWritten conclusions and a decrease in NoConc conclusions for comparisons in which the questioned writing contained only addresses. For additional details and discussion regarding the effects of amount and comparability of writing, see SI Appendix, Appendix G.When considering all QKsets included in the study (and not just restricted to the 32 pairs described above), the same general trends are observed, particularly with respect to content comparability. When the known writing contained the same content as the questioned writing, there was a notable increase in correct 3.8.United States v. Johnsted case . Using a majority of participants to assess the writing style of the Q in each QKset, 37% were disconnected printing, 29% were connected cursive, and the remaining 34% were considered “mixed” . We did not observe any association between writing style and rates of errors or incorrect conclusions. We detected one significant difference in conclusion rates: On mated QKsets in which the content of the questioned and known writing were the same, the conclusions reported for cursive samples were significantly more conservative than those for mixed or print samples . Conclusion rates did not vary significantly as a function of writing style for nonmated trials, or on mated trials with different content; there was no difference in rates for mixed vs. print writing. For further details and discussion regarding conclusions by writing style, see SI Appendix, Appendix L1.In the ted case , a federted case . Therefo4.SI Appendix, Appendix C2).The rates measured in this study are intended to provide estimates to inform decision-making and guide future research. In order to maximize the relevance of the reported rates, the samples were selected to span a range of quality, quantity, and attributes found in casework. A supermajority of participants responded that the samples in the study (both questioned and known) were representative of casework, and that the overall perceived difficulty of the comparisons in this study corresponded to casework  because they tended to give more definitive conclusions; FDEs with at least 2 y of formal training were less likely to make definitive conclusions, but, when made, those conclusions were more likely to be correct (higher PPV and NPV). The performance of participants varied widely in terms of rates of errors and of correct conclusions, as well as in proportions of definitive vs. qualified conclusions. Of the 86 participants, 42 made at least one erroneous Written vs. NotWritten). The results suggest that blind verification by a second examiner would be expected to detect most—but not all—erroneous conclusions prior to reporting, given that 7.9% of erroneous Written conclusions and 2.2% of erroneous NotWritten conclusions were reproduced. As shown in previous studies (Knowing one participant’s response is not a strong predictor of other participants’ responses: Participants reported exactly the same conclusion 40.4% of the time, but 84.5% of conclusions were reproduced within ±1 conclusion, suggesting that most of the variability between participants’ conclusions can be explained by differences in strengths of conclusions and generally does not indicate differences in assessments of authorship. Only 1.2% of the responses resulted in contradictory definitive conclusions ( studies , 33, a lNote that these results may not be representative of all forensic document casework, do not account for operational quality assurance such as technical review and verification, did not allow for consultation with other subject matter experts as needed, and did not allow for requests for additional known writing from contributors. The examination procedure used may differ from that used by some FDEs, particularly regarding the conclusion scale and use of digital images.This study was conducted for use by policy makers, laboratory managers, the legal community, FDEs, and the forensic science research community. These results may be used, in part, to assess the scientific validity of handwriting comparisons, to provide data for use in assessing changes in operational procedures, to enhance FDE training, and to enhance quality assurance procedures.Supplementary File


P = 0.002), and showed significantly larger radiologic tumor size (P = 0.036) than the control group. The mean tumor size was significantly decreased after imatinib treatment . There was no significant difference in resection margin involvement (P >0.999), and sphincter preservation rates (P = 0.627) between the two groups. No difference was observed with respect to morbidities, hospital stay, local recurrence and disease-free survival. Neoadjuvant imatinib treated group had similar propensity with control group after treatment. We thought reduced tumor sized could enhance resectability and provide more chance to preserve sphincter for rectal GIST patients. Considering large tumor size and higher rate of sphincter invasion in the neoadjuvant group, imatinib treatment could be helpful as a conversion strategy to make huge and low-lying rectal GIST operable and achieve better surgical outcomes.Although gastrointestinal stromal tumors (GISTs) are rare disease and rectal GISTs is only 5% of total GISTs, they have the worst prognosis. Due to narrow pelvis, tumor rupture or positive resection margin are common in the management of rectal GISTs. The impact of neoadjuvant treatment on the clinical outcomes of rectal gastrointestinal stromal tumors (GISTs) remains unclear. Thus, we conducted a retrospective study to investigate the impact of neoadjuvant imatinib on rectal GIST. The cohort comprised 33 patients; of them, 10 and 23 belonged to the neoadjuvant  and the control group , respectively. Neoadjuvant group was associated with more common levator ani muscle displacement ( Gastrointestinal stromal tumors (GISTs) are rare, with an annual incidence of 1/100,000, but they can occur at any site in the gastrointestinal tract . Among GImatinib  has been proven to be effective for the management of metastatic GISTs, including as adjuvant therapy after complete tumor excision , 8. FurtFor the surgical management of rectal GISTs, several specific factors should be considered. Tumor rupture or unsuccessful excision of tumor are highly aggressive prognostic factors and well-known risk factors for local recurrence in the management of GIST) , 12. DueWe evaluated patients who underwent surgical resection and were pathologically diagnosed with rectal GIST located within 15 cm of the anal verge between 2002 and 2014. Data were extracted from a maintained database. Two patients were excluded because of incomplete pathologic results. Finally, 33 patients were included in the analysis. Patients who underwent neoadjuvant imatinib treatment and those who underwent surgery without prior imatinib treatment were classified into the neoadjuvant group and the control group, respectively. This study was approved by the Institutional Review Board of Severance Hospital (IRB No.2019-0682-001) with a waiver of informed consent. This study was also followed to the ethical principles included in Declaration of Helsinki in 1964.All patients were preoperatively staged using abdominopelvic computed tomography (APCT) or pelvic magnetic resonance imaging (MRI). Tumor size was defined as the longest distance of the tumor as measured via APCT or pelvic MRI. We repeated APCT or MRI based on the 3–4 months schedule. The surgical treatment was recommended in case the treatment response was anticipated as maximum. Operative methods were decided according to tumor location and size, which were transanal excision with grossly negative margins or radical resection as a low anterior resection or abdominoperineal resection. Complete resection was defined as the removal of the entire tumor, with a negative resection margin. Lymph node resection was not necessary. Although surgical resection was regarded as the treatment of choice, imatinib treatment before resection was selected at the surgeon’s discretion, according to the tumor size or invasiveness to the adjacent organs or anal sphincter by preoperative APCT or MRI. In the neoadjuvant group, preoperative Imatinib was continued until the tumor no longer decreased in size on imaging studies. Surgical resection was planned if the tumor size failed to decrease further or when progression was observed during a regular follow-up.Postoperative tumor size and mitotic count were evaluated by pathologists. Risk classification was performed according to the National Institutes of Health consensus criteria  13]. Af. Af13]. t test and x2 test, respectively. Fisher’s exact test was used for between-group comparisons. Paired t-test was used to compare tumor sizes before and after neoadjuvant treatment. Disease-free survival (DFS) was calculated from the date of first diagnosis to the date of recurrence or the last follow-up date. LR and DFS were assessed using the Kaplan-Meier method. Multivariate analyses for LR and DFS were performed using the Cox proportional hazard model. All statistical analyses were performed using SPSS statistical software . Differences with P values of <0.05 were considered statistically significant.Continuous and categorical variables were analyzed using Student’s The cohort comprised 33 patients; of them, 10 and 23 were classified into the neoadjuvant group and the control group, respectively. All ten patients who underwent neoadjuvant imatinib treatment were confirmed to have rectal GIST via transanal biopsy before imatinib treatment.P = 0.002). The mean tumor size was significantly larger in the neoadjuvant group . After neoadjuvant treatment, the mean tumor size decreased significantly from 6.8 cm to 4.7 cm in the neoadjuvant group (P = 0.033)  grade, or tumor location from the anal verge between the two groups. Most of the tumors (31 (93.9%)) were located less than 5 cm from the anal verge. At the time of diagnosis, the rate of levator ani muscle displacement by the tumor on APCT or pelvic MRI was significantly higher in the neoadjuvant group than that in the control group (9 (90%) vs. 7 (31.8%), = 0.033) . The mea= 0.033) .P = 0.627). There was also no difference in resection margin involvement between the two groups (neoadjuvant vs. control: 9 (90.0%) vs. 19 (82.6%), P >0.999). With respect to difficulty of surgery, there was no difference in the rate of operation time (more than 4 hours) between the two groups. However, intraoperative blood loss >500 ml was more common in the neoadjuvant group than that in the control group (6 (60%) vs. 4 (17.4%), P = 0.035). Postoperative complications and hospital length of stay did not differ between the two groups. Most patients showed c-KIT mutations, and there was no difference in mutation frequencies between the two groups (10 (100%) in the neoadjuvant group vs. 22 (95.7%) in the control group, P = 0.351). Both groups showed a similar rate of risk stratification (P = 0.291) (The sphincter preservation rates did not differ between the two groups (neoadjuvant vs. control: 8 (80%) vs. 20 (87%), = 0.291) .P>0.999). Although there was no significance between the groups, patients underwent adjuvant treatment because of margin involvement (n = 4) and high risk (n = 2) in control group (P>0.999). In the neoadjuvant group, two patients underwent adjuvant treatment based on the physician’s decision, even though they had low risk after surgery  of patients in the neoadjuvant group and 26.1% (n = 6) of patients in the control group underwent adjuvant treatment with imatinib ( surgery .P = 0.76) (P = 0.011) and exon 11 mutations . In addition, the 5-year DFS was similar between the groups  (P = 0.037)  . In the  = 0.99) . In the = 0.037) .This study demonstrated that neoadjuvant imatinib treatment for large rectal GISTs could reduce tumor size and thus increase the resectability. In addition, it seems not to increase postoperative morbidity and seem not to deteriorate the oncologic outcomes such as resection margin positivity or long term oncologic outcomes.The National Comprehensive Cancer Network guideline recommends preoperative imatinib for metastatic disease or unresectable cases for which surgery would induce significant morbidity . NeverthIn this study, the duration of neoadjuvant imatinib treatment differed between patients, with a mean duration of 9.7 months. Although changes in tumor density detected on CT scans are known to predict tumor responses after imatinib treatment , 17, thiPreviously, it has been recommended to use imatinib whenever possible until the effect is insignificant , 18, 19.Another advantage of neoadjuvant treatment is achieving a negative resection margin through a conversion strategy. For rectal GISTs, the rate of positive resection margins is as high as 40% , and a pIn this study, there was one patient with a positive resection margin in the neoadjuvant group (10%), compared with four patients in the control group (17.4%). We demonstrated the comparison focused on rectal GIST patients and achieved a 90% rate of R0 resection in the neoadjuvant group. The similar resection margin involvement rate and the long-term LR rate indicate that neoadjuvant imatinib treatment can reduce the tumor size and increase its resectability. Therefore, if neoadjuvant imatinib can reduce the size of the tumor and limit its invasion to adjacent organs, it would facilitate complete surgical resection.In addition to tumor size, mitotic count is also an important risk factor and can determine the malignancy potential. Because mitotic count can be influenced by neoadjuvant imatinib, risk classification might be more accurate when it is evaluated using samples obtained before neoadjuvant treatment. Mutational analysis has recently been found to be essential because it helps exclude less sensitive or resistant tumors to imatinib treatment and allows proper dosing for patients with c-kit exon mutations , 23. FouThere are several potential limitations in this study. Because of the retrospective study design, we could not ignore selection bias on clinical outcomes. In addition, due to the rarity of rectal GISTs, the number of enrolled patients was relatively small. However, we demonstrated the effect of neoadjuvant imatinib focused on rectal GIST, whereas other studies did not. In our study, the application of neoadjuvant imatinib treatment was left to the surgeon’s decision and/or clinical applicability of imatinib. The use of imatinib in the neoadjuvant setting is not fully reimbursed by the National Health Insurance Corporation in Korea, and there is no standardized indication for performing curative resection. Different follow-up and imaging studies were applied to each patient during imatinib neoadjuvant treatment. Besides there were not enough patients’ functional outcome data or stoma reversal. Because of retrospective study, we could not also evaluate it additionally.In conclusion, the present study is a comparative analysis of preoperative imatinib treatment between those who underwent neoadjuvant imatinib treatment followed by radical resection and those who underwent surgery without prior imatinib treatment. Our findings showed that neoadjuvant imatinib treatment effected to reduce initial tumor size. Reduced tumor size might increase resectability and thus enhance chance of sphincter preservation for low-lying rectal GISTs. Therefore, neoadjuvant imatinib treatment was worthy of consideration as conversion strategy for huge and low-lying rectal GIST without deterioration long-term outcomes.S1 Data(CSV)Click here for additional data file.