Effect of prostate brachytherapy case volume in the community setting on oncologic outcomes.

Abstract

339 Background: A volume-outcome relationship has not yet been comprehensively established for prostate cancer brachytherapy, a treatment modality that is declining in usage, with regard to cancer-specific outcomes. The goal of this study is to describe the relationship between facility brachytherapy case volume and cancer-specific outcomes in patients with localized prostate cancer. Methods: We identified patients in CaPSURE (Cancer of the Prostate Strategic Urologic Research Endeavor) diagnosed with localized prostate cancer between 1999-2007 and treated with brachytherapy. Only community hospital settings had sufficient documented cases for inclusion. The brachytherapy case volume of each facility was based on its total number of brachytherapy-treated prostate cancer patients with facilities above the 75th percentile categorized as high-volume facilities. The primary outcome was biochemical failure based on the Phoenix definition or receipt of salvage treatment after primary brachytherapy. We used logistic regression to compute a propensity score for on high vs low volume facility based on demographic, clinical, and treatment variables. Cumulative incidence of biochemical failure and prostate cancer specific mortality of patients were assessed with lifetable estimates, log-rank test, and Cox proportional hazards regression, adjusted for propensity score and case volume. Secondary outcomes included patient-reported UCLA Prostate Cancer scores for urinary, sexual, and bowel function and bother. Results: We identified 1,282 patients with localized prostate cancer treated with brachytherapy between 1999-2007 across 18 community facilities with median follow-up of 9 years. The median number of brachytherapy cases over the 8 study years was 210. 722 patients (56.3%) received brachytherapy at high-volume (>210 cases) community facilities and 560 patients (43.7%) at low-volume (10-210 cases) facilities. High-volume facilities predominantly used Pd-103 seeds while low-volume facilities predominantly used I-125 seeds. A greater proportion of patients at low-volume facilities had pre-brachytherapy hormone therapy (47% vs 26%; p<0.01). Cumulative incidence of biochemical failure at 10 years was 10.3% for high-volume facilities and 12.5% for low-volume facilities (p=0.27). Cumulative incidence of prostate cancer specific mortality at 10 years was 4.0% for high-volume facilities and 4.5% for low-volume facilities (p=0.62). Patient-reported scores of urinary, sexual, and bowel bother at 6 months following brachytherapy were comparable between the two groups. Conclusions: Patients with localized prostate cancer treated with brachytherapy at high-volume community facilities have similar rates of biochemical failure, prostate cancer specific mortality, and trends in quality of life outcomes compared to those treated at low-volume community facilities.