Cancer-specific and other-cause mortality after radical prostatectomy versus observation in patients with prostate cancer: Competing-risks analysis of a large North American population-based cohort

Background: Initial treatment options for low-risk clinically localized prostate cancer (PCa) include radical prostatectomy (RP) or observation. Objective: To examine cancer-specific mortality (CSM) after accounting for other-cause mortality (OCM) in PCa patients treated with either RP or observation. Design, setting, and participants: Using the Surveillance Epidemiology and End Results Medicare-linked database, a total of 44 694 patients ≥65 yr with localized (T1/2) PCa were identified (1992-2005). Intervention: RP and observation. Measurements: Propensity-score matching was used to adjust for potential selection biases associated with treatment type. The matched cohort was randomly divided into the development and validation sets. Competing-risks regression models were fitted and a competing-risks nomogram was developed and externally validated. Results and limitations: Overall, 22 244 (49.8%) patients were treated with RP versus 22450 (50.2%) with observation. Propensity score-matched analyses derived 11 669 matched pairs. In the development cohort, the 10-yr CSM rate was 2.8% (2.3-3.5%) for RP versus 5.8% (5.0-6.6%) for observation (absolute risk reduction: 3.0%; relative risk reduction: 0.5%; p <0.001). In multivariable analyses, the CSM hazard ratio for RP was 0.48 (0.38-0.59) relative to observation (p <0.001). The competing-risks nomogram discrimination was 73% and 69% for prediction of CSM and OCM, respectively, in external validation. The nature of observational data may have introduced a selection bias. Conclusions: On average RP reduces the risk of CSM by half in patients aged ≥65 yr, relative to observation. The individualized protective effect of RP relative to observation may be quantified with our nomogram.