about 40  % of all tumors located in the posterior fossa are low - grade astrocytomas [ 7 , 15 , 17 ] .
when these tumors are totally resected , the prognosis is very favorable with more than 90  % of patients being cured without additional treatment . the overall survival rate for children who had gross total resection of low - grade gliomas
was reported to be 99  % . however , after incomplete resection , the prognosis is unpredictable [ 5 , 10 , 13 ] . in many cases , the tumors will progress ; however , in some cases , the tumor will have arrested growth or even tumor regression will occur [ 5 , 10 ] . relatively little attention has been paid in the literature in determining the incidence of arrested growth or spontaneous regression after partial resection of low - grade cerebellar astrocytomas and documenting such cases in detail .
there is controversy about whether patients with tumor remaining after surgery should receive radiation therapy .
it is also unclear whether only patients with incomplete resection require follow - up and for how long .
because of the lack of information on arrested growth and tumor regression after incomplete resection of low - grade cerebellar astrocytomas in children , the aim of this study was to provide more information on these phenomena by reviewing cases of patients with cerebellar astrocytoma who underwent surgery at our hospital .
we reviewed all cases of patients under 16  years of age who were diagnosed with cerebellar astrocytoma and underwent surgery at kaohsiung medical university hospital from january 1983 to december 2011 .
medical charts , imaging findings , operative notes , histopathological reports , and survival times of 12 patients with cerebellar astrocytoma were reviewed for the purpose of evaluating the patients prognosis ; patients lost to follow - up were excluded .
the clinical data for the 12 patients in this study are summarized in table  1 .
six patients were boys and six were girls . their age at the time of diagnosis ranged from 3 to 16  years .
nine patients ( 75  % ) presented with gait disturbance , eight ( 66.7  % ) with headache , six ( 50  % ) with vomiting , and four ( 33.3  % ) with a visual problem . the tumor was located in the midline in seven patients ( 58.3  % ) , in the left cerebellum in three patients ( 25  % ) and in the right cerebellum in two patients ( 16.7  % ) .table 1clinical features of 12 children with cerebellar astrocytomacase no.age at diagnosis ( years)gendertumor sitesurgeryhistologyradiotherapymalignant transformationvp shuntreoperationoutcomefollow - up ( years)115mmidlinesubtotalgr i++ ( gr i to gr ii)+after 2  yearsdeceased at age 382329fmidlinesubtotalgr i++ ( gr i to gr iii)+after 15  yearsgood25315fleft cerebellumsubtotalgr ii+after 8  yearsgood2443fleft cerebellumtotalgr iafter 4  yearsgood21515mmidlinetotalgr ii+good20616fleft cerebellumsubtotalgr i+after 6  yearsgood18714mleft cerebellumtotalgr igood1887mmidlinesubtotalgr ii+good1695mmidlinesubtotalgr igood12106fmidlinesubtotalgr i+after 2  yearsgood101116fright cerebellumtotalgr igood91210mright cerebellumtotalgr igood3 clinical features of 12 children with cerebellar astrocytoma the tumor was totally removed in five patients ( 41.7  % ) whereas seven patients ( 58.3  % ) had only partial tumor removal .
there were no signs of type 1 neurofibromatosis such as neurofibromas or caf au lait spots over the body .
histological examination of surgical specimens showed that nine tumors were classic pilocytic astrocytoma ( grade i ) and three were diffuse ( grade ii ) astrocytoma .
one patient who had total resection ( case 4 ) and five patients who had partial resection ( cases 1 , 2 , 3 , 6 , and 10 ) underwent a second surgical operation .
in addition , three patients with subtotal resection , all of whom had the tumor located in the midline , received a ventriculoperitoneal shunt . among the seven patients who had incomplete tumor resection in the initial operation , five patients ( 71.4  % ) had tumor progression detected during follow - up and two patients ( 28.6  % )
did not have any tumor progression detected during follow - up of 17  years ( case 6 ) and 11  years ( case 9 ) .
the time at which progression occurred is indicated by time of reoperation in table  1 . in one of these two patients who did not have tumor progression
( case 9 ) , serial t1 mri with gadolinium demonstrated tumor regression from february 2008 to january 2011 with the tumor getting smaller ( fig . 
among the five patients who had total resection , one patient ( case 5 ) with diffuse astrocytoma ( grade ii ) received radiation therapy .
five of the patients with subtotal resection were treated with radiation therapy , which is still used in some hospitals for patients with subtotal resection of cerebellar low - grade astrocytomas .
post - irradiation follow - up of the patients irradiated for residual tumor revealed that in one patient ( case 1 ) there was malignant transformation from grade i to grade ii at 2  years after surgery and in another patient ( case 2 ) there was malignant transformation from grade i to grade iii ( anaplastic astrocytoma ) at 15  years after surgery .
one of the patients ( case 3 ) with partial tumor resection who was treated with radiation therapy developed radiation - induced anaplastic meningioma over the supratenorium after 23  years of follow - up ( fig . 
1serial brain mri scans of case 9 show regression of the cerebellar astrocytomafig . 2 
 a mri scan of case 3 reveals anaplastic meningioma over the supratenorium left parietal lobe .
b brain ct scan reveals total removal of the meningioma serial brain mri scans of case 9 show regression of the cerebellar astrocytoma 
 a mri scan of case 3 reveals anaplastic meningioma over the supratenorium left parietal lobe .
b brain ct scan reveals total removal of the meningioma among the 12 patients , 11 were alive at the end of the study .
one patient ( case 1 ) died of pneumonia 23  years after undergoing surgery .
the clinical data for the 12 patients in this study are summarized in table  1 .
six patients were boys and six were girls . their age at the time of diagnosis ranged from 3 to 16  years .
nine patients ( 75  % ) presented with gait disturbance , eight ( 66.7  % ) with headache , six ( 50  % ) with vomiting , and four ( 33.3  % ) with a visual problem . the tumor was located in the midline in seven patients ( 58.3  % ) , in the left cerebellum in three patients ( 25  % ) and in the right cerebellum in two patients ( 16.7  % ) .table 1clinical features of 12 children with cerebellar astrocytomacase no.age at diagnosis ( years)gendertumor sitesurgeryhistologyradiotherapymalignant transformationvp shuntreoperationoutcomefollow - up ( years)115mmidlinesubtotalgr i++ ( gr i to gr ii)+after 2  yearsdeceased at age 382329fmidlinesubtotalgr i++ ( gr i to gr iii)+after 15  yearsgood25315fleft cerebellumsubtotalgr ii+after 8  yearsgood2443fleft cerebellumtotalgr iafter 4  yearsgood21515mmidlinetotalgr ii+good20616fleft cerebellumsubtotalgr i+after 6  yearsgood18714mleft cerebellumtotalgr igood1887mmidlinesubtotalgr ii+good1695mmidlinesubtotalgr igood12106fmidlinesubtotalgr i+after 2  yearsgood101116fright cerebellumtotalgr igood91210mright cerebellumtotalgr igood3 clinical features of 12 children with cerebellar astrocytoma
the tumor was totally removed in five patients ( 41.7  % ) whereas seven patients ( 58.3  % ) had only partial tumor removal .
there were no signs of type 1 neurofibromatosis such as neurofibromas or caf au lait spots over the body .
histological examination of surgical specimens showed that nine tumors were classic pilocytic astrocytoma ( grade i ) and three were diffuse ( grade ii ) astrocytoma .
one patient who had total resection ( case 4 ) and five patients who had partial resection ( cases 1 , 2 , 3 , 6 , and 10 ) underwent a second surgical operation .
in addition , three patients with subtotal resection , all of whom had the tumor located in the midline , received a ventriculoperitoneal shunt . among the seven patients who had incomplete tumor resection in the initial operation , five patients ( 71.4  % ) had tumor progression detected during follow - up and two patients ( 28.6  % )
did not have any tumor progression detected during follow - up of 17  years ( case 6 ) and 11  years ( case 9 ) .
the time at which progression occurred is indicated by time of reoperation in table  1 . in one of these two patients who did not have tumor progression
( case 9 ) , serial t1 mri with gadolinium demonstrated tumor regression from february 2008 to january 2011 with the tumor getting smaller ( fig .  1 ) .
among the five patients who had total resection , one patient ( case 5 ) with diffuse astrocytoma ( grade ii ) received radiation therapy .
five of the patients with subtotal resection were treated with radiation therapy , which is still used in some hospitals for patients with subtotal resection of cerebellar low - grade astrocytomas .
post - irradiation follow - up of the patients irradiated for residual tumor revealed that in one patient ( case 1 ) there was malignant transformation from grade i to grade ii at 2  years after surgery and in another patient ( case 2 ) there was malignant transformation from grade i to grade iii ( anaplastic astrocytoma ) at 15  years after surgery .
one of the patients ( case 3 ) with partial tumor resection who was treated with radiation therapy developed radiation - induced anaplastic meningioma over the supratenorium after 23  years of follow - up ( fig . 
2 
 a mri scan of case 3 reveals anaplastic meningioma over the supratenorium left parietal lobe .
b brain ct scan reveals total removal of the meningioma serial brain mri scans of case 9 show regression of the cerebellar astrocytoma 
 a mri scan of case 3 reveals anaplastic meningioma over the supratenorium left parietal lobe .
b brain ct scan reveals total removal of the meningioma among the 12 patients , 11 were alive at the end of the study .
one patient ( case 1 ) died of pneumonia 23  years after undergoing surgery .
in this study , we analyzed the long - term follow - up results of 12 patients with childhood cerebellar astrocytoma : five of whom had total tumor resection and seven of whom had subtotal tumor resection . as expected , total tumor removal was an important prognostic factor .
however , two patients with subtotal resection did not have tumor progression and one of these patients had spontaneous tumor regression which was well documented on serial mri .
half of the patients , including five with subtotal resection were treated with radiation therapy .
we found that complete resection of cerebellar astrocytoma is an important prognostic factor , indicating a more favorable prognosis than subtotal resection .
this was also the conclusion of a much larger study by villarejo et al .   who reviewed 203 cases of low - grade cerebellar astrocytoma .
they also found that that location , size , and histology of tumors have a significant effect on prognosis ; the tumors located in one hemisphere , that are small in size , and are either cystic or have a cystic posterior nodule have a better prognosis .
however , beebe et al .   in a study of 103 children with low - grade cerebellar astrocytomas found that cognitive and adaptive outcome was not related to tumor location . in a prospective study of 518 children with low - grade glioma , wisoff et al .
they found that the only factor that was highly predictive of progression - free survival in multivariate analysis was gross total resection ; location , histological type , and age were not significant independent predictors of progression - free survival .
a number of studies have looked at various measurements of outcomes in patients with cerebellar astrocytomas , although without considering whether tumors were completely resected or not during surgery . in a study that looked at not only neurological outcomes of surgery but also behavioral and emotional adjustment and health - related quality of life ( hrqol ) in children with low - grade cerebellar astrocytomas , it was found that although 43  % of patients had neurological sequelae , 19  % had cognitive deficits that caused significant problems in schools , and 27  % had emotional adjustment disturbances , the patients rated their hrqol as normal or in some instances actually higher than healthy controls .
in contrast , it has been reported that in patients treated for low - grade astrocytoma , qol was significantly decreased in every domain except for emotions .
it has also been found that in patients with cerebellar astrocytoma who were treated surgically , during follow - up ranging from 1  year to almost 9  years , numerous deficits in various combinations and different degrees were detected including apraxia , motor neglect , and dysarthric characteristics plus other deficits such as language , memory , and behavioral problems .
the authors noted that whereas cerebellar pilocytic astrocytoma is generally considered to be a benign tumor that is associated with a good long - term quality of life , they found that following surgical treatment it results in long - term neurocognitive disturbances resulting in a high percentage of children needing special education .
galloway et al .   studied 370 consecutive patients with solid tumors or leukemia who were treated with curative radiotherapy .
they found that 18 second tumors occurred in 16 patients and , that during long - term follow - up , the risk for second tumor does not plateau .
the authors concluded that despite the risk of a second tumor the primary threat to survival is failure to control the primary tumor and therefore radiotherapy should be used selectively . in our study , six patients received radiotherapy and two cases ( cases 1 and 2 ) had malignant transformation of tumor , and another ( case 3 ) had radiation - induced anaplastic meningioma develop over the supratenorium .
radiation - induced meningiomas have been reported in the literature [ 4 , 9 ] .
we do not recommend radiation therapy for partial resection of childhood cerebellar astrocytoma because it has not been demonstrated in most studies to reduce the rate of recurrence or prolong overall survival .
it should be noted , however , that hadjipanavis et al .   found radiotherapy to be useful for treating patients with recurrent or subtotal resection of pilocytic astrocytoma .
we also do not recommend radiotherapy because cerebellar astrocytomas are insensitive to radiation therapy and there is a risk of radiation - induced necrosis as well as second malignancy .
the rate of malignant transformation was very high in our study ( 33.3  % ) , especially considering that such transformation is considered to be a rare event .
one possibility is a biopsy sampling error 2  years after surgery . for patients who have tumor progression , surgery for tumor removal
our study showed that after partial excision a small proportion of cerebellar astrocytomas do not progress or even regress . among the seven patients in our study with partial resection , in one
there was arrested growth and in another there was regression ; the other five patients had progression . these phenomena of arrested growth and regression have been reported in a number of studies [ 5 , 7 , 1114 ] .
.   found that among 50 residual cerebellar astrocytomas , 16  % demonstrated arrested growth and 32  % demonstrated spontaneous regression .
as have a number of other authors , we recommend a  wait and see  policy for patients with partial resection in which the patients are followed up with mri [ 5 , 7 , 11 , 12 ] .
the mechanism of spontaneous regression of cerebellar astrocytoma is unknown . among the various mechanisms suggested
have been immunologic mechanisms , induction of differentiation , and elimination of a carcinogen , ischemic tumor necrosis , and apoptosis .
.   found that the mean time for tumor regression in their series was 13.6  months which led them to suggest that the mechanism involved ischemic necrosis and/or apoptosis .
.   showed that an apoptosis marker , apoptag , was positive within the cerebellar astrocytoma of a patient with tumor regression , which was an indication that the mechanism of regression may have involved the apoptosis - related genes .
assessment of long - term outcome did not include evaluation of cognitive function , emotional disturbances , behavior disorders , educational problems , or hrqol .
we have documented that patients with subtotal removal of cerebellar astrocytoma can have arrested tumor growth or spontaneous tumor regression during long - term follow - up . following partial resection of pediatric cerebellar astrocytoma
, we recommend that the patients be followed up a  wait and see  approach with surveillance using mri .
we found that several tumors treated with radiotherapy after surgery had malignant transformation and do not recommend adjuvant radiation treatment for children with cerebellar astrocytoma who have subtotal resection .
more research is needed on the prognosis of patients with subtotal resection of cerebellar astrocytoma .
 purposethe prognosis of children with low - grade cerebellar astrocytoma who have partial resection of tumor is largely unpredictable . 
 the purpose of this study was to review the long - term outcome of such patients.methodsthe medical charts , imaging findings , operative notes , histopathological reports , and survival times of 12 patients with cerebellar astrocytoma were reviewed.resultsfive patients had total resection and seven had partial resection . 
 nine patients had grade i histology and three patients had grade ii . 
 follow - up duration ranged from 3 to 25  years . among the seven patients with residual tumor , five had tumor progression , one had arrested tumor growth , and one had spontaneous tumor regression . 
 five patients with partial resection received radiotherapy and three had malignant transformation of tumor during follow - up . 
 six patients , including five who had partial resection , underwent a second operation . 
 one patient with partial resection died of pneumonia 23  years after surgery.conclusionspatients with complete tumor resection had a better prognosis than patients with partial resection . for patients with partial resection 
 , we recommend a  wait and see  policy with surveillance using mri . 
 the phenomenon of arrested tumor growth and spontaneous tumor regression in patients with cerebellar astrocytoma who have subtotal resection warrants further study . 