neoadjuvant chemotherapy ( nac ) has generally been used in treatment of locally advanced and inflammatory breast cancer , but its use is increasing for earlier stages of the disease [ 1 - 3 ] .
the number of patients who are candidates for breast conserving treatment ( bct ) increases with the use of nac , which downsizes tumors , facilitating bct in patients who would otherwise require mastectomy .
several clinical trials have reported equivalent impacts of neoadjuvant versus adjuvant chemotherapy on survival . the locoregional recurrence ( lrr ) rate was also acceptably low in patients treated with nac followed by breast conserving surgery ( bcs ) and radiotherapy ( rt ) .
dna microarray analysis of gene expression profiles has divided breast cancer into distinct molecular subtypes with different clinical outcomes and responses to treatment , including estrogen receptor ( er)positive / luminal , basal - like , and her2-positive subtypes . however , dna microarray analysis has challenges for wide use in routine clinical care , determination of molecular subtypes based on clinically available immunohistochemical ( ihc ) markers such as hormone receptor ( hr ) and her2 status has been considered and validated as a more practical approach to identification of the corresponding subgroups based on gene expression profiling .
it has been demonstrated that different molecular subtypes can predict lrr in addition to survival and distant metastasis ( dm ) in the adjuvant setting [ 10 - 12 ] .
however , the impact of molecular subtypes on ipsilateral breast tumor recurrence ( ibtr ) and lrr in patients who undergo nac warrants further investigation .
therefore , the current study was conducted to evaluate whether molecular subtypes can identify patients at high risk for ibtr and lrr following nac and bct .
this was a single - institution retrospective review of an institutional review board  approved prospective breast cancer database .
a total of 335 consecutive patients with non - metastatic breast cancer who underwent nac followed by bcs and rt from 2002 to 2009 were identified . before initiation of nac
, all patients had been clinically staged according to the sixth edition of the american joint committee on cancer ( ajcc ) guidelines .
clinical stages were evaluated by physical examination , ultrasonography , fluorodeoxyglucose - positron emission tomography ( pet)/computed tomography ( ct ) , and chest ct .
clinicopathological data were recorded , including age , menopause status , ct stage , cn stage , pathological tumor size , number of lymph nodes ( lns ) identified pathologically , histological type , histological grade , er , progesterone receptor ( pr ) , her2 , and ki-67 status .
nac consisted of anthracycline - based ( doxorubicin 60 mg / m and cyclophosphamide 600 mg / m every 3 weeks for four cycles , n=150 ) , taxane - based ( docetaxel 75 mg / m and capecitabine 1,000 mg / m orally twice daily on days 1 - 14 every 3 weeks for four cycles , n=85 ; paclitaxel 80 mg / m followed by gemcitabine 1,200 mg / m on days 1 and 8 every 3 weeks for four cycles , n=27 ) , or combined anthracycline - taxane  based therapy ( doxorubicin 60 mg / m and cyclophosphamide 600 mg / m every 3 weeks for four cycles followed by docetaxel 100 mg / m every 3 weeks for four cycles , n=73 ) .
a total of 245 patients ( 73.1% ) were treated in one of the two prospective institutional clinical trials .
nac regimen for the remainder was chosen at physician s discretion . in the bcs procedure ,
residual primary tumors were excised , and clear margins to healthy tissues were determined from frozen biopsy specimens . however , five patients with persistent positive resection margins in the final pathology reports declined further surgical resection .
no further revision surgery was attempted in 30 patients with close resection margins ( < 2 mm ) .
standard level i and ii axillary ln dissections were performed in all except 14 patients who underwent sentinel ln biopsy without axillary dissection .
no residual tumor or only carcinoma in situ in both primary breast tumor and lns was considered pathologic complete response ( pcr ) . following bcs ,
rt was performed with tangential fields at a median dose to the breast of 50.4 gy in 28 fractions over 5.5 weeks in all patients .
all patients received an electron boost to the tumor bed with a median dose of 10 gy in five fractions .
supraclavicular nodal rt was delivered in 318 patients ( median dose , 45 gy in 25 fractions ) .
internal mammary nodal rt was administered at a median dose of 55 gy to only seven patients with pre - nac initial pet - positive internal mammary lns .
adjuvant hormone suppression therapy was offered to all patients with er - positive or pr - positive tumors .
some patients showed changes in er and pr expression before and after nac , but hormonal suppression therapy was administered to all patients whose tumors were er- or pr - positive in one or more tests . following rt ,
an ihc assay was used to evaluate the expression of the er , pr , her2 , and ki-67 markers in pretreatment core biopsies . er and pr positivity were defined using the allred score when strong nuclear staining was observed in at least 3/8 tumor cells examined . er and pr status were categorized as hr - positive when er or pr staining was positive , and as hr - negative when er and pr staining were negative .
immunostaining for her2 was considered positive in the case of strong ( 3 + ) membranous staining in at least 10% of tumor cells , or in the case of 2 + with unequivocal amplification by fluorescence in situ hybridization . for evaluation of ki-67 ,
areas with the highest ki-67 staining were examined ; 15% was used as the cut - off value for ki-67 to dichotomize the patients . according to the ihc features on core biopsies before nac ,
patients were classified according to ihc - based molecular subgroups as follows : luminal a ( hr+/her2/ki-67 < 15% ) , luminal b1 ( hr+/her2/ki-67  15% ) , luminal b2 ( hr+/her2 + ) , her2 ( hr/her2 + ) , and triple negative ( tn ) ( hr/her2 ) .
in this study , the her2 group , which is known as an unfavorable feature , was divided into two subtypes based on the use of trastuzumab .
the final six groups were as follows : luminal a , luminal b1 , luminal b2 , her2 with trastuzumab ( her2[t+ ] ) , her2 without trastuzumab ( her2[t ] ) , and tn .
lrr was defined as recurrent disease in the ipsilateral breast , chest wall or axillary , supraclavicular , infraclavicular , or internal mammary lns .
all ibtrs and lrrs were considered events , regardless of whether they were the first site of failure versus occurred with or after dm .
patients who did not experience ibtr or lrr were censored at the last follow - up or at the time of death .
distributions of the clinical factors among groups were compared using the kruskal - wallis test for continuous variables and the chi - square test for categorical variables .
actuarial rates of ibtr and lrr were calculated using the kaplan - meier method , and differences between groups were compared using the two - sided log - rank test .
logistic regression was used to evaluate the association between covariates of interest and the probability of ibtr or lrr .
significant differences in the distribution of histological type , histological grade , resection margin status , and response to nac were observed among subtypes . in evaluation of the response to nac
, we noted a difference ( p < 0.01 ) in pcr rates with a lower percentage of patients in the luminal a ( 10.6% ) and b1 ( 6.1% ) subgroups compared with patients in the her2(t ) ( 35.5% ) , and tn ( 23.0% ) subgroups .
the median follow - up period was 7.2 years ( range , 0.7 to 11.6 years ) .
twenty - six ibtrs , 15 regional recurrences , 67 dms , and 56 deaths occurred during follow - up ( table 2 ) .
the 5-year lrr - free survival rates in the subtypes were as follows : luminal a , 96.4% ; b1 , 93.9% ; b2 , 90.3% ; her2(t+ ) , 92.9% ; her2(t ) , 78.3% ; and tn , 79.6% ( fig .
compared with the luminal a subtype , significantly higher lrr rates were observed for the luminal b2 , her2(t ) , and tn subtypes ( p=0.02 , p < 0.01 , and p < 0.01 , respectively ) .
the 5-year ibtr - free survival rates in the subtypes were as follows : luminal a , 97.2% ; b1 , 93.9% ; b2 , 92.8% ; her2(t+ ) , 92.9% ; her2(t ) , 89.1% ; and tn , 84.6% ( fig .
the her2(t ) and tn subtypes had significantly higher rates of ibtr compared with the luminal a subtype ( p=0.04 and p < 0.01 , respectively ) . despite the same unfavorable molecular markers with her2(t ) , her2(t+ ) subtype showed no difference in ibtr and lrr rates compared with the luminal a subtype . the 5-year dm - free and disease - free survival ( dfs )
rates were as follows : luminal a , 90.2% ; b1 , 75.6% ; b2 , 83.0% ; her2(t+ ) , 85.7% ; her2(t ) , 76.6% ; and tn , 75.4% ( fig .
1c ) and luminal a , 88.4% ; b1 , 75.6% ; b2 , 81.9% ; her2(t+ ) , 85.7% ; her2(t ) , 70.0% ; and tn , 72.1% ( fig .
the clinicopathological variables associated with ibtr and lrr were analyzed by univariate and multivariate analyses ( table 3 ) . in univariate analysis ,
the factors affecting ibtr development included the tn subtype ( p < 0.01 ) , poorly differentiated tumors ( p=0.03 ) , and clinical t3 - 4 stage ( p < 0.01 ) .
luminal b2 subtype ( p=0.03 ) , her2(t ) subtype ( p < 0.01 ) , tn subtype ( p < 0.01 ) , poorly differentiated tumor ( p=0.01 ) , and clinical t3 - 4 stage ( p < 0.01 ) were also associated with lower lrr - free survival rates . in the multivariate model , the her2(t )
subtype , tn subtype , and clinical t3 - 4 stage affected the development of both ibtr and lrr . compared with the luminal a subtype , the her2(t ) and
tn subtypes were potent factors affecting ibtr / lrr , with hazard ratios of 4.2 ( p=0.04)/7.6 ( p < 0.01 ) and 6.9 ( p=0.01)/8.1 ( p < 0.01 ) , respectively ( table 3 ) .
notably , a pcr after nac was not associated with the development of ibtr ( p=0.39 ) or lrr ( p=0.65 ) .
patients of the her2(t+ ) subtype had significantly lower hazard ratios for ibtr and lrr compared with her2(t ) patients . in the analysis of ibtr and lrr according to pcr versus non - pcr after nac , patients of the tn subtype who failed to achieve pcr showed a significantly higher lrr ( p=0.03 ) ( fig .
however , among patients of the non - tn subtypes , including her2(t ) , no significant effect of a pcr on either lrr ( p=0.52 ) ( fig .
breast cancer is now regarded as a biologically heterogeneous disease comprising different molecular subtypes , each with a different prognosis and response to treatment [ 10 - 12 ] .
these subtypes , including luminal , her2 , and basal - like , can be defined by gene expression profiling   or approximations to this classification using ihc .
clinicians should consider these features for proper assessment of the relevant evidence and decide on an appropriate therapeutic course of action . in a series of women with clinical stage ii - iii breast cancer who underwent nac and bct
, we found that molecular subtypes showed correlation with different rates of ibtr and lrr .
the tn and her2(t ) subtypes had worse outcomes with significantly higher ibtr and lrr rates than those of other subtypes despite excellent tumor responses to nac .
several authors have examined the impact of molecular subtype on lrr in different patient populations .
nguyen et al .   evaluated 793 patients treated with bct as a first - line intervention .
after a median follow - up period of 70 months , the 5-year lrr rate was 0.8% for luminal a , 8.4% for her2 , and 7.1% for basal subtypes .
also evaluated differences in lrr according to subtype in patients undergoing bct as initial treatment .
these patients were classified based on receptor status as well as nuclear grade , with subgroups defined as luminal a ( hr+/her2/grade 1 - 2 ) , luminal b ( hr+/her2/grade 3 ) , luminal her2 ( hr+/her2 + ) , her2 ( hr/her2 + ) , and tn ( hr/her2 ) . the 5-year lrr rates were 0.8% for luminal a , 10.8% for her2 , and 6.7% for tn subtypes .
in contrast to our study , both of these studies were limited to patients undergoing initial surgery .
after a median follow - up period of 43 months , 5-year lrr rates were 3.8% , 1.3% , and 4.2% for luminal a , her2 , and basal subtypes , respectively .
the molecular subtype and pcr predicted dm , dfs , and overall survival ( os ) .
only patients who received nac were included ; however , patients underwent bct or mastectomy .
after a median follow - up period of 55 months , a higher rate of lrr in patients with basal ( 14% ) versus luminal ( 4% ) or her2 ( 5% ) tumors was reported . by evaluating only the 49 patients who underwent bct ,
no lrr events were observed in the luminal or her2 groups , while 8% of the basal group developed lrr .
most recently , caudle et al .   analyzed the clinicopathological data from 595 patients who received nac and bct .
after a median follow - up period of 64 months , the 5-year lrr - free survival rates were found to vary by subtype : hr+/her2 , 97.0% ; hr+/her2 + , 95.9% ; hr/her2 + , 86.5% ; and hr/her2 , 89.5% ( p=0.001 ) .
first , our data encompassed a homogeneous group of patients with clinical stage ii - iii breast cancer who underwent nac followed by bct at a single institution , compared with the results from patients treated with nac followed by bct or mastectomy .
to the best of our knowledge , the current study is unique in its analysis of the impact of molecular subtypes on ibtr and lrr in patients who underwent nac followed by only bct , which could be associated with the concerns regarding a higher lrr rate compared with mastectomy .
most previous studies have focused on dfs , os , or lrr alone [ 23,26 - 28 ] .
inclusion of patients from previous treatment eras may yield higher rates of lrr compared with those treated more recently due to several factors .
the evolution of systemic therapy has resulted in better local control and better outcomes on systemic recurrence .
the use of modern radiation techniques and the evolution of breast imaging may have an impact on the rates of ibtr and lrr .
third , we included 36 patients treated with trastuzumab , of whom 14 her2(t+ ) patients had a better local outcome compared with her2(t ) patients .
five - year ibtr- and lrr - free survival rates were 92.9% versus 89.1% and 92.9% versus 78.3% in her2(t+ ) versus her2(t ) , respectively .
this result suggests that the use of trastuzumab could alter the impact of the molecular subtype on local outcome in her2 subtype patients .
last , we found that a pcr to nac had no impact on locoregional outcomes in any patients of non - tn groups . in tn patients , however , a pcr was associated with excellent ibtr and lrr control .
the association between the extent of response to nac and prognosis has been examined [ 3,5,23,25 - 27 ] .
the best relative dfs , as well as dm - free survival , and os   was observed in those who achieved a pcr .
reported that a pcr to nac did not affect lrr or ibtr regardless of subtype , while caudle et al .   reported that patients achieving a pcr had similar lrr rates among subtypes
a second limitation was the modest number of patients evaluated ; categorization according to the six subtypes resulted in a small number of patients in some subtypes , including her2(t+ ) , luminal b1 , and her2(t ) patients .
therefore , these findings should be confirmed in a larger prospective study in the future .
in conclusion , we demonstrated that the tn and her2 subtypes predicted higher rates of ibtr and lrr after nac followed by bct . among the non - tn
subtype patients , pcr was not predictive of better ibtr or lrr . however , among the tn subtype patients , a pcr to nac was a predictor of better lrr control .
taken together , a novel locoregional treatment strategy to decrease ibtr and lrr such as mastectomy instead of bct in tn subtype patients with non - pcr to nac deserves further investigation .
improvements in systemic therapy , investigation of radiosensitizing agents , radiation dose escalation , and other new techniques may prove to be important .
 purposethe purpose of this study is to determine whether breast cancer subtype can affect locoregional recurrence ( lrr ) and ipsilateral breast tumor recurrence ( ibtr ) after neoadjuvant chemotherapy ( nac ) and breast - conserving therapy ( bct).materials and methodswe evaluated 335 consecutive patients with clinical stage ii - iii breast cancer who received nac plus bct from 2002 to 2009 . 
 patients were classified according to six molecular subtypes : luminal a ( hormone receptor [ hr]+/her2/ki-67 < 15% , n=113 ) , luminal b1 ( hr+/her2/ki-67  15% , n=33 ) , luminal b2 ( hr+/her2 + , n=83 ) , her2 with trastuzumab ( her2[t+ ] ) ( hr/her2+/use of trastuzumab , n=14 ) , her2 without trastuzumab ( her2[t ] ) ( hr/her2 + , 
 n=31 ) , and triple negative ( tn ) ( hr/her2 , n=61).resultsafter a median follow - up period of 7.2 years , 26 ibtrs and 37 lrrs occurred . 
 the 5-year lrr - free survival rates were luminal a , 96.4% ; b1 , 93.9% ; b2 , 90.3% ; her2(t+ ) , 92.9% ; her2(t ) , 78.3% ; and tn , 79.6% . 
 the 5-year ibtr - free survival rates were luminal a , 97.2% ; b1 , 93.9% ; b2 , 92.8% ; her2(t+ ) , 92.9% ; her2(t ) , 89.1% ; and tn , 84.6% . in multivariate analysis , her2(t ) 
 ( ibtr : hazard ratio , 4.2 ; p=0.04 and lrr : hazard ratio , 7.6 ; p < 0.01 ) and tn subtypes ( ibtr : hazard ratio , 6.9 ; p=0.01 and lrr : hazard ratio , 8.1 ; p < 0.01 ) were associated with higher ibtr and lrr rates . a pathologic complete response ( pcr ) 
 was found to show correlation with better lrr and a tendency toward improved ibtr controls in tn patients ( ibtr , p=0.07 ; lrr , p=0.03).conclusionthe tn and her2(t ) subtypes predict higher rates of ibtr and lrr after nac and bct . 
 a pcr is predictive of improved ibtr or lrr in tn subtype . 