Treatment of Low-risk Prostate Cancer with Radical Hypofractionated Accelerated Radiotherapy with Cytoprotection (HypoARC): An Interim Analysis of Toxicity and Efficacy

Abstract

Aim: Radiobiological analysis of clinical data suggests that prostate cancer has a low alpha/beta ratio, implying that large radiotherapy fractions may better control the disease. Acceleration of radiotherapy may be also of importance in a subset of tumors. In this study we assessed the feasibility and efficacy of a highly accelerated and hypofractionated scheme of radiotherapy (HypoARC), for the treatment of localized low risk prostate cancer. Patients and Methods: Fifty-five patients with prostate cancer (T1-2 stage, Gleason score <7 and prostate specific antigen (PSA) <10 ng/ml) were treated with localized conformal 4-field radiotherapy to the prostate and seminal vesicles: 51 Gy were delivered (3.4 Gylfraction, within 19 days). The biological dose to the prostate ranged from 67.9-91.7 Gy. Amifostine (0-1000 mg depending upon tolerance) was delivered daily for cytoprotection. The median follow-up of patients is 30 (6-69) months. Results: Early toxicity was overall low, proctitis being the most frequent side-effect (23.6% grade II). High dose amifostine significantly protected against proctitis (p=0.005). Grade 2 frequency and dysurea occurred in 1.8% and 3.7% of cases, respectively. There was no late toxicity >= grade 2. Amifostine significantly protected against chronic frequency (p=0.02). Within a median follow-up of 30 months, one patient (1.8%) experienced a biochemical relapse. Conclusion: HypoARC is feasible and safe for patients with low-risk prostate cancer and, considering also the high efficacy noted, a strong rationale is provided for the further evaluation of HypoARC in randomized trials.