Prognostic value of comorbidity measures among Australian men with non-metastatic prostate cancer

Aim: To compare the utility of various admission-based comorbidity indices in men diagnosed with non-metastatic prostate cancer. Methods: The study cohort consisted of men diagnosed with prostate cancer between January 2002 and December 2020 according to the state-wide South Australian Cancer Registry. Comorbid conditions were captured for 11,470 men through linkage to public hospital admission data 5-years prior to prostate cancer diagnosis. The comorbidity indices evaluated included the Charlson Comorbidity Index (CCI), Elixhauser Co-morbidity Index (ECI), National Cancer Institute (NCI) comorbidity index, and Cancer, Care and Comorbidity (C3) index. The predictive performance of the four indices for 5-year overall mortality was compared using the C-statistic from Cox proportional hazard models adjusted for age, socioeconomic status, and year of prostate cancer diagnosis. Results: Approximately 31 %, 45 %, 28 % and 47 % of patients had at least one comorbid condition captured by CCI, ECI, NCI and C3, respectively. Regarding the prediction of 5-year overall survival, CCI (c-index = 0.763) slightly higher predictive performance than ECI (0.758), NCI (0.755), and C3 (0.754). Indices in their continuous score resulted in better predictive performance than them being used categorically (0, 1, and 2 +). The NCI (continuous score) showed a stronger association with overall mortality (hazard ratio (HR) 2.47, 95% CI:2.29-2.67) than the other indices, despite its predictive performance being lower than the CCI and ECI. Conclusion: There were only slight differences in the predictive accuracy among the indices, with the CCI having a slightly better prognostic value than the other indices. All four indices demonstrated a strong association with mortality in men diagnosed with prostate cancer.