Epidemiology and economic burden of brain metastases among patients with primary breast cancer: results from a US claims data analysis

To estimate the incidence, prevalence, and economic burden of secondary breast cancer brain metastases (BCBM) among a US-based population of patients with primary breast cancer. Female patients diagnosed with secondary BCBM between 1/2002 and 12/2004 and with a brain or head diagnostic test within 30 days of the BCBM diagnosis were identified in a US commercial insurance claims database. A 12-month look-back period was used to identify patients with a breast cancer diagnosis and those with and without a history of BCBM. Patients were required to be continuously enrolled in their health plan for the duration of the study. Incident BCBM patients were matched to a control group of breast cancer patients with no evidence of BCBM. Patient characteristics at baseline, incidence and prevalence rates, and resource utilization and health care costs were determined. From 2002 to 2004, 779 incident and 995 prevalent BCBM patients and 8,518 primary breast cancer patients were identified. The incidence of BCBM during this time period was 9.1% (95% CI = 8.5%, 9.8%); the prevalence of BCBM was 11.7% (95% CI = 11.0%, 12.4%), with rates increasing from 2002 to 2004. About 22% of incident patients died (based on a proxy measure) during the follow-up period, an average of 158 days (95% CI = 131.1, 183.9) from the index BCBM diagnosis. A 1:1 match of incident BCBM patients to controls resulted in 775 patients in each group. At 6 months follow-up (N = 398), incident BCBM patients had significantly more hospital stays (mean 1.1 vs. 0.5, P