Ten-Year Outcomes and Toxicity with 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 efficacy and toxicity outcomes of patients treated with intensity modulation radiation therapy (IMRT) for localized prostate cancer with 70 Gy in 28 fractions at 2.5 Gy/fraction. This IRB-approved study included all 854 consecutive patients with localized prostate cancer treated with moderately hypofractionated IMRT at a single institution between 1998 and 2012. The median follow-up was 11.3 years (maximum, 19 years). Patients were grouped into low-risk (LR, n=266); favorable intermediate-risk (FIR), defined as a single National Comprehensive Cancer Network (NCCN) intermediate-risk factor (n=238); unfavorable intermediate-risk (UIR), defined as ≥2 NCCN intermediate-risk factors (n=106), and high-risk (HR, n=244) groups. Biochemical relapse free survival (bRFS; defined as nadir + 2 ng/mL), clinical relapse free survival (cRFS), & overall survival (OS) were analyzed used Kaplan-Meier analysis. Prostate cancer specific mortality (PCSM) was analyzed using Fine and Gray regression. All grade ≥3 genitourinary (GU) and gastrointestinal (GI) toxicities were recorded using CTCAE version 4.03 and cumulative incidence rates of GU and GI toxicity were calculated. The 10-year bRFS was 71% (95% CI: 67-74%). For patients with LR, FIR, UIR, and HR disease the 10-year bRFS rates were 88%, 78%, 71%, and 42%, respectively (p <0.0001), while the 10-year cRFS rates were 95%, 91%, 85%, and 72%, respectively (p <0.0001). Overall, the 10-year actuarial OS rate was 69% (95% CI: 66-73%) and the 10-year PCSM was 7% (95% CI: 5-9%). 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 for localized prostate cancer continues to show excellent oncological outcome with a low incidence of toxicity over long-term follow up. This fractionation schedule appears to be acceptable for patients across all risk groups.