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

Abstract

Purpose: 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 70 Gy in 28 fractions at 2.5 Gy per fraction.

Methods and materials: 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.

Results: The median follow-up was 11.3 years (maximum, 19 years). 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.

Conclusions: 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.