Moderate Hypofractionation in High-Risk, Organ-Confined Prostate Cancer: Final Results of a Phase III Randomized Trial

Abstract

Purpose To report the final results on treatment outcomes of a randomized trial comparing conventional and hypofractionated radiotherapy in high-risk, organ-confined prostate cancer (PCa). Patients and Methods This single-institution, randomized clinical trial, conducted from January 2003 to December 2007, enrolled 168 patients with high-risk PCa who were randomly assigned in a 1:1 ratio to conventional (80 Gy in 40 fractions in 8 weeks) or hypofractionated radiotherapy (62 Gy in 20 fractions in 5 weeks) to prostate and seminal vesicles. The primary outcome measure was late toxicity. Additional outcomes were freedom from biochemical failure (FFBF), prostate cancer–specific survival (PCaSS), and overall survival (OS), evaluated on an intention-to-treat basis. Results A total of 85 patients were assigned to conventional and 83 to hypofractionated radiotherapy. At a median follow-up of 9 years (interquartile range, 7.5 to 10.1 years), no differences was observed in physician-assessed late gastro intestinal and genitourinary toxicity greater than or equal to grade 2 ( P = .68 and .57, respectively) were found between the two arms. The 10-year FFBF rate was 72% in the hypofractionation group and 65% in the conventional fractionation group ( P = .148). Ten-year OS rates were 75% in the hypofractionation group and 64% in the conventional group, respectively ( P = .22). The same features for 10-year PCaSS were 95% and 88%, respectively ( P = .066). Hypofractionation, pretreatment prostate-specific antigen level, Gleason score, and clinical tumor stage for FFBF, and hypofractionation and Gleason score for PCaSS were significant prognostic variables on the multivariate analysis. Conclusion Long-term findings showed that hypofractionated radiotherapy failed the intent of either reducing physician-assessed late toxicity or maintaining the same efficacy. A postrandomization analysis, however, revealed that hypofractionation was a significant prognostic factor for FFBF and PCaSS, when adjusted for clinical prognostic variables.