Prediction of Other-Cause Mortality in Older Patients with Breast Cancer Using Comorbidity

SIMPLE SUMMARY: Selecting older patients for adjuvant breast cancer treatments is challenging as its benefits can be diminished by shorter life expectancies. In addition to age, comorbidity increases the risk of dying from other causes than breast cancer. Available prediction tools have either not adjusted for individual comorbidities or have shown inaccurate predictions when a higher number of comorbidities are present. Up to now, an optimal comorbidity score to be used in prediction tools has not been established. Therefore, this study aimed to assess the predictive value of the Charlson comorbidity index for other-cause mortality and to compare these predictions with using a simple comorbidity count. We found that the Charlson index performed similarly as comorbidity count. The use of comorbidity count in the development of new prediction tools for older patients with breast cancer is recommended as its simplicity enhances the tool’s applicability in clinical practice. ABSTRACT: Background: Individualized treatment in older patients with breast cancer can be improved by including comorbidity and other-cause mortality in prediction tools, as the other-cause mortality risk strongly increases with age. However, no optimal comorbidity score is established for this purpose. Therefore, this study aimed to compare the predictive value of the Charlson comorbidity index for other-cause mortality with the use of a simple comorbidity count and to assess the impact of frequently occurring comorbidities. Methods: Surgically treated patients with stages I-III breast cancer aged ≥70 years diagnosed between 2003 and 2009 were selected from the Netherlands Cancer Registry. Competing risk analysis was performed to associate 5-year other-cause mortality with the Charlson index, comorbidity count, and specific comorbidities. Discrimination and calibration were assessed. Results: Overall, 7511 patients were included. Twenty-nine percent had no comorbidities, and 59% had a Charlson score of 0. After five years, in 1974, patients had died (26%), of which 1450 patients without a distant recurrence (19%). Besides comorbidities included in the Charlson index, the psychiatric disease was strongly associated with other-cause mortality (sHR 2.44 (95%-CI 1.70–3.50)). The c-statistics of the Charlson index and comorbidity count were similar (0.65 (95%-CI 0.64–0.65) and 0.64 (95%-CI 0.64–0.65)). Conclusions: The predictive value of the Charlson index for 5-year other-cause mortality was similar to using comorbidity count. As it is easier to use in clinical practice, our findings indicate that comorbidity count can aid in improving individualizing treatment in older patients with breast cancer. Future studies should elicit whether geriatric parameters could improve prediction.