Stereotactic body radiotherapy (SBRT) versus conventional fractionated intensity-modulated radiotherapy (CF-IMRT) for patients with early-stage localized prostate cancer: One-year late toxicity results from a prospective randomized phase II study.

Abstract

27 Background: It remains uncertain whether stereotactic body radiotherapy (SBRT) is superior to conventional fractionated intensity-modulated radiotherapy (CF-IMRT) in the treatment of early-stage prostate cancer. Here we report the 1-year late toxicity results from this randomized phase II study comparing SBRT and CF-IMRT. Methods: The primary endpoint of this single centre randomized phase II study is the health-related quality of life (HRQOL), as measured by the bowel and urinary domains of the Expanded Prostate Cancer Index Composite (EPIC) instrument. The secondary endpoints include toxicities, biochemical control and overall survival. We enrolled low and intermediate risk localized prostate cancer patients (T1-T2, Gleason score ≤7 and PSA <20). Patients were randomly assigned in a 1:1 ratio to receive either CF-IMRT with 38 fractions of 2 Gy in 7.5 weeks (five fractions per week) or SBRT with 5 fractions of 7.25 Gy in 2 weeks (three fractions per week). Neoadjuvant androgen-deprivation treatment is optional for the intermediate risk patients. A 1-year late adverse event is defined as the first occurrence of worst severity of the adverse event within 1 year after the completion of RT, and it was evaluated with the Common Terminology Criteria for Adverse Events (version 4.0). Patient recruitment was completed in May 2017. Results: Between Jan 2015 and May 2017, 68 patients were recruited and 4 patients were not eligible. 64 patients were randomized to treatments with SBRT (n=31) or CF-IMRT (n=33). At 1- year follow-up, two grade 3 genitourinary (GU) late toxicities, one in each arm (3%), were reported. SBRT patients experienced significantly less ≥ grade 1 late gastrointestinal (GI) toxicities (SBRT vs IMRT: 64% vs 84%, p=0.041) and similar ≥grade 1 late GU toxicities (SBRT vs IMRT: 93% vs 100%, p=0.2307) to IMRT patients. Conclusions: SBRT results in significantly less 1-year late GI toxicities than CF-IMRT in with low and intermediate risk prostate cancer. The study is registered at ClinicalTrials.gov (NCT02339701). Clinical trial information: NCT02339701.