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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Radiation Oncology, Brigham and Women's Hospital/Dana-Farber Cancer Institute, Boston, MA. Electronic address: michael.xiang@post.harvard.edu.
Michael
M
Xiang
Department of Radiation Oncology, Brigham and Women's Hospital/Dana-Farber Cancer Institute, Boston, MA.
Paul L
PL
Nguyen
D000368:Aged; D001918:Brachytherapy; D006801:Humans; D008297:Male; D057216:Propensity Score; D016016:Proportional Hazards Models; D017430:Prostate-Specific Antigen; D011471:Prostatic Neoplasms / Q000401:mortality* / Q000532:radiotherapy*; D012307:Risk Factors; D018426:SEER Program; D015996:Survival Rate; D014481:United States / Q000453:epidemiology
D017430:Prostate-Specific Antigen
Brachytherapy; Prostate cancer; Radiation therapy