Impact of comorbidity on outcome of older breast cancer patients: a FOCUS cohort study.

Older breast cancer patients often suffer from comorbid diseases, which may influence life expectancy. The aim of this study was to assess the impact of specific comorbidities on overall survival and distant recurrence free period (DRFP) of older breast cancer patients. Patients were included from the population-based FOCUS cohort which contains 3,672 breast cancer patients aged 65 years or older. The impact of comorbidity on overall survival and DRFP was analyzed using multivariable Cox proportional hazard models and Poisson regression models. Median follow-up time was 6.8 years (range 0-14.0). Irrespective of age; the number of comorbid diseases was significantly associated with worse overall survival [hazard ratio (HR) per increasing number of comorbid diseases: 1.20, 95 % confidence interval (CI) 1.13-1.27 and HR 1.09, 95 % CI 1.05-1.13 for age <75 and age ≥ 75, respectively]. Median follow-up time for DRFP was 5.7 years (range 0-14.0). An increasing number of comorbid diseases was associated with a decreasing risk of metastases among patients aged ≥ 75 (HR 0.94, 95 % CI 0.87-1.02), whereas an increasing risk was shown for patients aged <75 (HR 1.09, 95 % CI 1.01-1.19). This study shows that in older breast cancer, patients overall survival and DRFP are influenced by comorbidity. This reiterates that patient outcome is not only influenced by breast cancer, and non-cancer-related factors should be taken into account.