Hypofractionated Radiation Therapy to the Prostate Bed With Intensity-Modulated Radiation Therapy (IMRT): A Phase 2 Trial

Abstract

Purpose: Postoperative radiation therapy (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 and Materials: In this phase 2 trial, patients submitted to radical prostatectomy were treated with hypofractionated RT to the prostate bed (adjuvant or salvage). The prescribed dose was 51 Gy in 15 fractions (3.4 Gy per fraction), using intensity modulated and image guided radiation therapy 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, cancer-specific survival, overall survival, and health-related quality of life. Results: Of 64 enrolled patients, 61 received radiation therapy (57 salvage and 4 adjuvant radiation therapy). After a median follow-up of 16 months, 11.5% of patients experienced acute grade >= 2 GU symptoms and 13.1% experienced acute grade >= 2 GI symptoms. The late grade >= 2 GU toxicity rate was 8.2%, and 1 patient (1.6%) developed both acute and late grade 3 GU 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 our ability to perform a robust oncologic endpoint assessment; however, the 2-year BFFS, use of subsequent salvage therapy, and the development of metastasis were 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.