Objective: 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.
Methods: 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.
Results: 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<0.001) and remained hospitalized for a longer period (mean 8.0 days vs. 2.5 days, P<0.001) compared to controls. Incident BCBM patients also averaged more physician office visits (32.8 vs. 24.3, P<0.001) as well as pharmacy claims (56.0 vs. 39.1, P<0.001). Similar differences were found at 12 months (N=230). Average total costs for incident BCBM patients at 6 months were $60,045 compared to $28,193 for controls (P<0.001); this difference was driven by higher mean inpatient ($17,462 vs. $5,362, P<0.001) and outpatient ($26,209 vs. $11,652, P<0.001) costs among incident BCBM patients. At 12 months, higher mean total costs persisted in incident BCBM patients ($99,899 vs. $47,719, P<0.001). After adjusting for key variables, mean costs for these patients were 123% higher than those for control group patients.
Conclusions: Secondary BCBM is a common occurrence among breast cancer patients, with rates increasing over time. Breast cancer patients with secondary BCBM incurred significantly more health care resources following diagnosis compared to those with breast cancer but no BCBM. Mean total costs for BCBM patients were more than double those of patients without BCBM at 6 and 12 months. The increasing prevalence and economic burden associated with BCBM suggests an unmet need that could be filled with newer treatments that improve breast cancer outcomes, including the prevention or delay of BCBM.