Long-term Efficacy Analysis Of Radiation Therapy For Unresectable Or Residual Pilocytic Astrocytoma

BackgroundPilocytic astrocytoma(PA)is assigned to the World Health Organization(WHO)grade 1.Pilocytic astrocytoma accounts for approximately 15%of central nervous system(CNS)tumors and is the most common primary brain tumor in children between 5 an 14 years of age,and the second most common in children between 0-4 and 15-19 years of age.The incidence continues to decrease into adulthood.Generally,pilocytic astrocytoma is a very slowly progressing astrocytic tumor that can be cured by total resection.The treatment of choice for these is surgery which yields recurrence-free survival rates higher than 90%after gross total resection.However,it is difficult to totally resect tumors in the midline brain structures including the diencephalon.In cases where gross total resection is not feasible,only half of patients remain progress-free.Conventional treatment consists of conservative surgery,partial removal or biopsy,and postoperative local irradiation.For patients with unresectable or residual tumors that demonstrate progression,additional therapies are indicated and radiotherapy(RT)is considered standard therapy.Although RT has been considered the most definitive and efficacious treatment for these unresectable or residual tumors,there are few data to support this claim.To examine the efficacy of radiation therapy for pilocytic astrocytoma,we retrospectively reviewed the experience at our institution.PurposeTo observe the prognosis of unresectable or residual Pilocytic astrocytoma treated with Radiation therapy and to explore the related influential factors.MethodsForty-eight patients 18years old or younger with unresectable or residual tumors have been treated since 2001.All patients had pathologic confirmation of diagnosis.All of a patient's clinical information and dose information were collected to analyze the relationship between the factors mentioned above and PFS or OS.All patients were treated with local fields including gross tumor plus a 1-2cm margin to a median dose of 54Gy with a daily fraction size of 1.8-2.0Gy.The independent-samples T test,chi-square test,Kaplan-Meier method,Log-rank test and the Cox-regression model were adopted in statistic.ResultForty-eight patients(thirty-three male and fifteen females)with unresectable or residual pilocytic astrocytomas underwent radiation therapy between 2001 and 2016.The median age was 11.5 years(range4-63years).Initial management included postoperative local irradiation(N=31)and only radiation(N=17).The median radiation target volume was 5.9 cm3.At a median follow-up of 36.5 months(rang9.0-178 months),five patients died and forty-three patients were alive.The progression free survival after radiation therapy for the entire series was 95.8%,78.2%,66.5%and 52.6%at 1,3,5 and 10 years,respectively.The overall survival after radiation therapy for the entire series was 100%,91.8%,86.7%and 77.1%at 1,3,5 and 10 years,respectively.No radiation-induced complications were observed.On univariate analysis:the follow factors have favorable influence on PFS:age,radiation target volume.Only radiation target volume has favorable influence on OS.On multivariate analysis age and target volume have favorable influence on PFS.But multivariate analysis no factor has favorable influence on OS.ConclusionThe result of this prospective trial confirm that patients with unresectable or residual pilocytic astrocytoma have a favorable prognosis with regard to PFS and OS.Radiation therapy need offer to patients with unresectable or residual tumor.