Radiotherapy delays malignant transformation and prolongs survival in patients with IDH-mutant gliomas

Objective:IDH-mutant lower-grade gliomas(LGGs,grade 2 or 3)eventually transform into secondary grade 4 astrocytomas(sAIDHmut/G4).Here,we sought to describe the transformation time,risk factors,and outcomes in malignant transformation of IDHmutant LGGs.Methods:We screened data for 108 patients with sAIDHmut/G4 in the Chinese Glioma Genome Atlas who had initial IDH-mutant LGGs and underwent reoperation during 2005–2021.We evaluated the transformation time from IDH-mutant LGGs to sAIDHmut/G4,and associated risk factors and outcomes.Malignant transformation was defined as pathological confirmation of grade 4 astrocytoma.Results:The median age of the 108 patients with IDH-mutant LGGs was 35 years(range,19–54);the median age at transformation was 40 years(range,25–62);and the median follow-up time for all patients was 146 months(range,121–171).The average transformation time was 58.8 months for all patients with LGGs(range,5.9–208.1);63.5 and 51.9 months for grade 2 and 3 gliomas,respectively;and 58.4 and 78.1 months for IDH-mutant/1p/19q-non-codeleted astrocytomas and IDH-mutant/1p/19q-codeleted oligodendrogliomas,respectively.Univariate and multivariate analysis indicated that radiotherapy[hazard ratio(HR),0.29;95%confidence interval(CI),0.137–0.595;P=0.001]and non-A blood type(HR,0.37;95%CI,0.203–0.680;P=0.001)were protective factors against delayed malignant transformation.Radiotherapy was associated with improved survival after transformation(HR,0.44;95%CI,0.241–0.803;P=0.008),overall survival(HR,0.50;95%CI,0.265–0.972;P=0.041),and progression-free survival(HR,0.25;95%CI,0.133–0.479;P<0.0001)in patients with IDH-mutant gliomas.Conclusions:Radiotherapy is associated with delayed malignant transformation and improved survival in patients with IDHmutant gliomas.