Does timing of androgen deprivation influence radiation-induced toxicity? A secondary analysis of Radiation Therapy Oncology Group protocol 9413

4655 Background: We conducted a secondary analysis of RTOG 9413 to compare if the timing of antiandrogen-therapy, concomitant versus adjuvant, influences the incidence of rectal toxicity in whole pelvic radiotherapy. Methods: For the purpose of this secondary analysis, we analyzed the 2 of the 4 arms of the study, in which all patients received radiotherapy to the whole pelvis followed by a boost to the prostate and excluded the two arms that received prostate only radiotherapy. The 2 arms differed only in the timing of the total of 4 months of total androgen deprivation (TAD): arm I (320 patients), TAD was begun 2 months before the start of radiotherapy and continued during radiotherapy. Arm III (319 patients), TAD started immediately after the completion of radiotherapy. Both acute rectal and acute urinary toxicities (CTC v.2.0), testosterone (measured at baseline and yearly after) and other patients data were modeled using the multivariate logistic regression and the multivariate Cox-proportional hazar...