10-yr Survival and Toxicity Outcomes of Stereotactic Body Radiotherapy for Prostate Cancer: A Nonrandomized Clinical Trial

Stereotactic body radiotherapy (SBRT) is established as standard therapy for organ-confined prostate cancer (PC) based on 5-yr phase 2-3 outcomes, but 10-yr data are lacking. Here, we report 10-yr results of a trial conducted at 21 centers. Patients were treated from January 2008 to April 2010. SBRT was delivered on a noncoplanar robotic platform with real-time motion management, to a total dose of 40 Gy in five fractions. Adjuvant hormone therapy was not allowed. Late toxicities (>90 d) were assessed with Common Terminology Criteria for Adverse Events version 3 (CTCAE v3). Biochemical failure is defined as nadir+2. Relapses are defined as biochemical or clinical failure or salvage/systemic PC therapy. Out of 310 evaluable patients, median age 68 yr; 172 were low-risk (LR), and 138 patients were intermediate-risk (IR). Median follow-up was 9 yr. Ten-yr cumulative grade 3 gastrointestinal (GI) or genitourinary (GU) toxicities were 1.4% and 1.5% in the LR and IR cohorts, respectively. There were no grade 4-5 events observed. Ten year grade 2+ GI and GU toxicity rates were 2.1% and 14% respectively. Overall survival in 10 yr was 84%. Overall, relapse-free survival (RFS) was 90%; 94% in the LR cohort, 86% in the IR cohort, and 92% versus 77% in the favorable vs unfavorable intermediate subgroups. In this multi-institutional trial, the 10-yr follow-up demonstrates that prostate SBRT yields minimal toxicity and favorable RFS.