Hypofractionated Radiotherapy for Prostate Cancer (HRT20) Trial: Results

Abstract

Radiotherapy is a definitive standard treatment for men with localized prostate cancer. Improvements in technology allow higher doses of radiation delivered to the prostate in less days, with lower doses to surrounding healthy tissues trying to reduce side effects. Several studies demonstrated that hypofractionated radiotherapy of 60 Gy is non-inferior to conventional radiotherapy fractionation. To report the first results in toxicity and biochemical relapse free survival of HRT20 trial after 5 years of recruitment. The HRT20 trial is registered (NCT03851926). A prospective observational study enrolled 298 men with localized prostate cancer (pT1b-T3aN0M0) started in October 2016. Median age was 75 (53-91). Median PSA was 14.5ng/ml. Using NCCN classification: 12,6% were low risk, 50.5% were intermediate and 36.9 % were high risk patients. The median duration of the treatment was 30 days (23-41) The clinical target volume (CTV) consisted of the prostate and seminal vesicles when affected. The CTV-planning target volume (PTV) margin was 0.8 cm. The primary end point evaluated assessed by CTCAE 4.0 was related later adverse events and the second end point was biochemical relapse free survival by Phoenix definition. WMAT plans calculations were carried out using the Monaco TPS version 5.10 based on a single arc arrangement. Univariate and multivariate logistic analyses were carried out. After median follow up of 56 months. The 5-year incidence rates of grade 2 and 3 late gastrointestinal toxicities were 6.3% and 3.1%, respectively, and those of grade 2 and 3 late genitourinary toxicities were 7.9% and 1%, respectively. PTV volume was found to be correlated with late rectal bleeding (p = 0.02). Also, urinary tract obstruction was correlated with PTV volume. The proportion of patients who were biochemical failure free at 5 years was 88·3% (95% CI 86·0-90·2) Multivariate analysis indicated that risk stage (p = 0.03) and number of positive needles biopsy cores (p = 0.02) were prognostic factor for biochemical relapse-free survival rates. The findings of this study indicate that hypofractionated is well tolerated and it is associated with good 5-years tumor-control outcomes in patients with localized prostate cancer. Long-term follow-up continues.