Ten-Year Outcomes of Moderately Hypofractionated (70 Gy in 28 fractions) Intensity Modulated Radiation Therapy for Localized Prostate Cancer

Abstract

Long-term outcomes with hypofractionated radiation therapy for prostate cancer are limited. We report 10-year outcomes for patients treated with intensity modulated radiation therapy (IMRT) for localized prostate cancer with 70Gy in 28 fractions at 2.5Gy per fraction. The study included 854 consecutive patients with localized prostate cancer treated with moderately hypofractionated IMRT and daily image guidance at a single institution between 1998 and 2012. Patients with a single intermediate risk factor were considered to have favorable intermediate-risk (FIR) disease, and those with multiple intermediate risk factors were considered unfavorable (UIR). Biochemical relapse-free survival, clinical relapse-free survival, and overall survival were analyzed using Kaplan-Meier analysis. Prostate cancer-specific mortality (PCSM) was analyzed using competing risk regression. All grade ≥3 genitourinary (GU) and gastrointestinal (GI) toxicities were recorded using Common Terminology Criteria for Adverse Event version 4.03, and cumulative incidence rates of GU and GI toxicity were calculated. The median follow-up was 11.3years (maximum, 19years). For patients with low-risk (LR), FIR, UIR, and high-risk (HR) disease, the 10-year biochemical relapse free survival rates were 88%, 78%, 71%, and 42%, respectively, (P<.0001). The 10-year clinical relapse free survival were 95%, 91%, 85%, and 72% for patients with LR, FIR, UIR, and HR, respectively, (P<.0001). For all patients, the 10-year actuarial overall survival rate was 69% (95% confidence interval, 66%-73%), and the 10-year PCSM was 6.8% (95% confidence interval, 5.1%-8.6%) overall. For patients with LR, FIR, UIR and HR disease, the 10-year PCSM rates were 2%, 5%, 5%, and 15%. Long-term grade ≥3 GU or GI toxicity remained low with 10-year cumulative incidences of 2% and 1%, respectively. High-dose moderately hypofractionated IMRT with daily image guidance for localized prostate cancer demonstrates favorable 10-year oncologic outcomes with a low incidence of toxicity. This fractionation schedule appears to be acceptable for patients across all risk groups.