Weighted Versus Unweighted Charlson Score to Predict Long-term Other-cause Mortality in Men with Early-stage Prostate Cancer

Abstract

BackgroundClinicians need a simple yet accurate method to predict other-cause mortality to inform medical decision making for men with prostate cancer (PCa). ObjectiveTo compare weighted and unweighted Charlson Comorbidity Index scores in predicting long-term, other-cause mortality in men with early-stage PCa. Design, setting, and participantsA retrospective cohort study of 1482 men with early-stage PCa diagnosed in 1998–2004 at two Southern California Veterans Affairs medical centers. Outcome measurements and statistical analysisSubhazard ratios and cumulative incidence of other-cause mortality associated with weighted and unweighted Charlson scores, calculated by competing-risks regression accounting for cancer mortality, along with Harrell concordance index (C-index) values. Results and limitationsWeighted and unweighted Charlson scores were identical in 88.6% of subjects (1313 of 1482 men) across all scores and in 91.7% of subjects (1359 of 1482 men) across scores of 0, 1, 2, and ≥3. In competing-risks analysis, hazards of other-cause mortality were similar when comparing weighted and unweighted scores. Men with weighted scores of 1, 2, and ≥3 (vs 0) had subhazard ratios of 2.3 (95% confidence interval [CI], 1.6–3.2), 4.1 (95% CI, 2.9–5.8), and 8.3 (95% CI, 5.9–11.5), respectively. Men with unweighted scores of 1, 2, and ≥3 (vs 0) had subhazard ratios of 2.5 (95% CI, 1.8–3.5), 4.5 (95% CI, 3.2–6.3), and 10.3 (95% CI, 7.2–14.7), respectively. The C-indexes for prediction of other-cause mortality were nearly identical for weighted scores (0.759 [95% CI, 0.715–0.780]) and unweighted scores (0.756 [95% CI, 0.717–0.780]). The difference in C-index between the two methods was −0.003 (95% CI, −0.01 to 0.004). ConclusionsAn unweighted Charlson score yields similar strength of association and variance in predicting long-term, other-cause mortality compared with a weighted Charlson score. Patient summaryA simple count of major comorbidities provides similar accuracy to a weighted index in predicting death from other causes in men with early-stage prostate cancer.