External Validation of a Nomogram for the Prediction of 10-year Life Expectancy in Candidates for Radical Prostatectomy

Purpose: Accurate life expectancy prediction is essential in decision-making concerning treatment of clinically localized prostate cancer (PCa). Nomogram predictions are more precise and reproducible than clinician's estimations. The most accurate nomogram addressing 10-year life expectancy in PCa patients has not been externally validated to date. Therefore, we aimed to evaluate the performance of this nomogram in a contemporary external cohort.

Patients And Methods: For this, we enrolled all consecutive patients, who underwent radical prostatectomy at a single institution between 2005 and 2007. Age at surgery and Charlson Comorbidity Index (CCI) were assessed. PCa-related deaths and patients under 55 years were excluded as indicated by the nomogram. The prediction of 10-year life expectancy was calculated according to the nomogram and compared to actual survival data. Calibration and discrimination were assessed using calibration plots.

Results: Overall, 1597 patients were evaluated, with a median age of 64 years (range 55-78 years) at surgery and a median follow-up of 134.4 months (range 0.1-161.7 months). Median CCI was 0 (range 0-10). At 10 years, 134 patients (8.4%) had died of other causes than PCa. The nomogram showed moderate discrimination capacities on receiver-operator characteristic analysis (c-index: 0.64). On calibration curves, the nomogram underestimated the actual life expectancy.

Conclusion: The performance accuracy of this prediction model was moderate and underestimated 10-year life expectancy of contemporary PCa patients. In conclusion, prediction of life expectancy remains challenging with a continued need for more precise tools.