An observational study of the prevalence and incidence of comorbid conditions in older women with breast cancer

Longitudinal analyses of comorbid conditions in women with breast cancer are few. Using Surveillance, Epidemiology, and End Results-Medicare data, we included 51 950 women aged >= 66 years with in situ and stage I to IV breast cancer diagnosed in 1998-2002. We identified the prevalence and incidence of 34 comorbid conditions in these women, as well as in a matched cohort without cancer whose rates were standardized to the age and race/ethnicity distribution of the cancer patients. We also estimated rates of office encounters and diagnostic or testing procedures during the 12 months before diagnosis. The prevalence of most conditions at diagnosis was comparable among breast cancer and noncancer patients. New conditions after diagnosis were more common in breast cancer patients, and the incidence rates increased with higher stage at diagnosis. Before diagnosis, women presenting with stage IV disease had 41% [95% confidence interval (CI) 38% to 43%] fewer physician encounters and 34% (95% CI 24% to 31%) fewer unique diagnostic tests than women diagnosed with carcinoma in situ. Many comorbid conditions are identified as a consequence of the breast cancer diagnosis. There appears to be an important contribution from a lack of interaction with the health care system before diagnosis.