Significant association of brachytherapy boost with reduced prostate cancer-specific mortality in contemporary patients with localized, unfavorable-risk prostate cancer

A randomized trial recently found that adding brachytherapy (BT) boost to external beam radiation therapy (EBRT) improves biochemical recurrence-free survival but not prostate cancer-specific mortality (PCSM).

We investigated the relationship between BT boost and PCSM in a modern cohort from a large population-based database.

We conducted an analysis of patients in Surveillance, Epidemiology, and End Results diagnosed with intermediate- or high-risk prostate cancer in 2004-2011, treated with EBRT only or EBRT + BT. The cumulative incidence of PCSM was evaluated in the presence of other-cause mortality as a competing risk. Propensity score matching and multivariable Fine and Gray proportional hazard models were used to evaluate the association of combined modality RT on PCSM.

A total of 52,535 patients were identified, of which 19. 6% were treated with EBRT + BT. One-third of cases were high-risk. On multivariable analysis, the adjusted hazard ratio (AHR) of PCSM for EBRT + BT vs. EBRT alone was 0. 69 (95% confidence interval [CI], 0. 55-0. 87, p = 0. 002), and the adjusted incidence of PCSM was 1. 8% vs. 2. 7% at 8 years, respectively. In subgroup analyses, the AHR for PCSM was also significantly reduced with EBRT + BT for high-risk disease (AHR 0. 70; 95% CI, 0. 52-0. 94, p = 0. 02; adjusted incidence of PCSM at 8 years, 5. 4% vs. 7. 6%), but not for intermediate-risk disease.

BT boost was associated with a moderate reduction to PCSM in men with localized unfavorable-risk prostate cancer. Those most likely to benefit are younger patients with high-risk disease.

Brachytherapy. 2015 Oct 17 [Epub ahead of print]

Michael Xiang, Paul L Nguyen

Department of Radiation Oncology, Brigham and Women's Hospital/Dana-Farber Cancer Institute, Boston, MA. Department of Radiation Oncology, Brigham and Women's Hospital/Dana-Farber Cancer Institute, Boston, MA.



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