Comorbidities in Medicare patients with and without breast cancer

6533 Background: Patients with comorbidities may be at increased risk for adverse effects from treatment. We used the SEER-Medicare linked dataset to see if patients with breast cancer had a higher prevalence and subsequent incidence (after diagnosis) of comorbid conditions compared to patients without breast cancer. Methods: We selected all women with breast cancer across all stages, diagnosed from 1998–2002 with follow up through 2005. Patients were at least 66 years old with at least 12 months of non-HMO Medicare coverage prior to diagnosis. One non-cancer patient was matched to each breast cancer patient on sex and county of residence, and was assigned the cancer diagnosis date of her matched subject. Comorbidities were identified through groups of comorbidity-specific International Classification of Diseases, 9th revision (ICD-9) codes used in Medicare claims. Claims only for diagnostic testing were excluded, and outpatient-based diagnosis codes were required to be present at least twice with at least 30 days in between to be included. Prevalence at baseline (%) and incidence rates (per 1,000 person-years) and their 95% confidence intervals were calculated for each comorbidity. Rates in the non-cancer group were standardized to the age and race distribution of the breast cancer group to control for potential confounding. Results: 52,977 cancer patients met the inclusion criteria. See table for prevalence and incidence estimates. Conclusions: Physicians should be aware that patients with breast cancer have higher prevalence and subsequent incidence of these comorbidities compared to non-cancer subjects. These differences may be related to the diagnostic process, as well as to therapies used in cancer treatment. [Table: see text] [Table: see text]