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

BackgroundInitial treatment options for low-risk clinically localized prostate cancer (PCa) include radical prostatectomy (RP) or observation.ObjectiveTo examine cancer-specific mortality (CSM) after accounting for other-cause mortality (OCM) in PCa patients treated with either RP or observation.Design, setting, and participantsUsing 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).InterventionRP and observation.MeasurementsPropensity-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 limitationsOverall, 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.ConclusionsOn 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.