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A randomized trial of a shorter radiation fractionation schedule for the treatment of localized prostate cancer.
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2016
Year
Treatment VerificationRadiation MedicineOncologyRadiation Therapy PlanningRandomized TrialClinical Radiation OncologyRadiation OncologyCancer ResearchHealth SciencesHypofractionation RtRadiation TherapyRadiological SciencesLocalized Prostate CancerProstatic DiseaseRadiologic ImagingComparative PlanningUrologyHigh Dose RadiotherapyMedicineSeminal Vesicles
5003 Background: Men with localized prostate cancer (PC) are often treated with high dose radiotherapy (RT) over 8-9 weeks. The α-β ratio which describes the dose-response of tumors and normal tissues to fractionated RT is low for PC. Hence, hypofractionation RT may be more efficacious in PC. Objective:To determine whether an 8-week course of escalated dose conformal RT can be compressed safely, and with similar efficacy into a 4-week course in intermediate risk PC. Methods: Men with intermediate risk PC (T1-2 Gleason 6 and PSA 10-20 ng/ml or T2b-c Gleason 6 and PSA < 20 ng/ml or T1-2 Gleason 7 and PSA < 20 ng/ml) were randomized to conventional (CON) RT, 78Gy in 39 fractions over 8 weeks or hypofractionated (HYP) RT, 60Gy in 20 fractions over 4 weeks, without hormone therapy. RT was planned to respect predefined dose constraints to a risk-adapted volume that included prostate +/- base of seminal vesicles. Daily image guidance was mandated and RT plans underwent real-time central review. The primary outcome is biochemical-clinical failure (BCF) defined by any of: PSA failure (nadir+2), hormonal intervention, clinical local or distant failure, or death. The trial was designed to show that the 5-year BCF of the HYP RT regimen is no higher than CON RT by up to 7.5% (hazard ratio [HR] up to 1.32) with 85% power and one-sided α = 5%. Acute and late GU/GI toxicity were assessed using RTOG criteria. Results:Between 2006 and 2011, 1,206 men from 27 sites in Canada, Australia and France were allocated to HYP RT (608) or CON RT (598). Mean age was 71 (48-88) years. Baseline characteristics were similar between arms. Median follow-up is 6.0 years. To date, 164 patients receiving HYP RT experienced a BCF event compared to 173 in the CON RT group. The BCF event rate at 5 years in both arms was 21%. The observed HR is 0.96 with 90% CI, 0.80 to 1.15. Overall 75 patients have died in each group. GU/GI toxicity grade > 3 was comparable in the acute period; however, late toxicity favored the HYPO RT arm: 3.5% vs. 5.4%, diff = -1.9%, 95% CI, - 4.3 to 0.43%. Conclusion: The HYP RT regimenwas not inferior to conventional RT with no increase in acute or late toxicity. Thus, it is a consideration for men with intermediate risk PC. Clinical trial information: NCT00304759.