Hypofractionated radiotherapy to the prostate bed with intensity modulated radiation therapy (IMRT): a phase II trial

Abstract Background Postoperative radiotherapy (RT) is a common therapy used for patients with prostate cancer. Although clinical trials have established the safety and efficacy of hypofractionation as a primary therapy, there are limited data in a postoperative setting. We conducted a prospective trial to evaluate the safety and feasibility of postoperative hypofractionated RT to the prostate bed. Methods In this phase II trial, patients submitted to radical prostatectomy (RP) were treated with hypofractionated RT to the prostate bed (adjuvant or salvage). The prescribed dose was 51Gy in 15 fractions (3.4 Gy per fraction), using IMRT and IGRT techniques. The primary endpoint was the rate of acute genitourinary (GU) grade > 2 toxicity. Secondary endpoints included: acute gastrointestinal (GI) and late GU/GI toxicities, biochemical failure-free survival (BFFS), metastasis-free survival (MFS), cancer specific survival (CSS), overall survival (OS) and health-related quality of life (HRQOL). Results 61 of 64 enrolled patients received radiotherapy (57 salvage and 4 adjuvant radiotherapy). After a median follow-up of 16 months, 11.5% of patients experienced acute GU grade > 2 symptoms and 13.1% experienced acute Grade ≥2 GI symptoms. The late GU grade > 2 toxicity rate was 8.2%; and 1 patient (1.6%) developed acute and late GU grade 3 toxicity. The late grade ≥2 GI toxicity rate was 11.5% and no grade 3 GI adverse events were reported. The short follow-up limits robust oncologic endpoint assessment, however, the 2-year BFFS, use of subsequent salvage therapy, and the development of metastasis was 95.1%, 0%, and 0%, respectively. Conclusions Hypofractionated RT to the prostate bed in 15 treatments was safe with an acceptable GU and GI toxicity profile. Further study in large randomized trials is warranted.