Ultra-hypofractionated radiation therapy for unfavourable intermediate-risk and high-risk prostate cancer is safe and effective: 5-year outcomes of a phase II trial.

Abstract

To report toxicity (primary endpoint) and biochemical disease-free survival (BDFS) outcomes of a phase II trial evaluating ultra-hypofractionated radiation therapy (UHRT), focusing on patients with unfavourable intermediate-risk and high-risk prostate cancer (PCa). From 2012 to 2017, 154 patients (92 with unfavourable intermediate-risk or high-risk PCa) were treated with helical TomoTherapy delivering 43.8-45.2 Gy in eight fractions over 3 weeks. Of these, 73% received hormonotherapy (51% neoadjuvant). The median (range) follow-up was 48 (19-84) months. For the whole series, crude BDFS and 5-year BDFS rates were 97.4% and 94.3%, respectively. The corresponding figures for unfavourable intermediate-risk and high-risk PCa were 96.7% and 90%, respectively. The crude metastasis-free survival rate was 98% for the unfavourable intermediate-risk and high-risk group. For the whole series, the 5-year cumulative urinary/intestinal grade 2+ late toxicity was 17.8/7.4%. No grade 4-5 toxicity was observed. One patient experienced late grade 3 toxicity (urinary). This eight-fraction UHRT regimen can be safely delivered to patients with unfavourable intermediate-risk/high-risk PCa. Its relapse rates are similar to those reported for the combination of external beam radiotherapy plus brachytherapy, however, the observed toxicity profile is milder. The disease survival rates compare favourably with historical controls in some other forms of radiotherapy, with similar side effects. Since the low rate of biochemical/metastasis relapse is encouraging, further research to confirm these results is justified.