Survival among elderly metastatic breast cancer patients in the United States.

Abstract

e16500 Background: The main objective is to assess predictors of survival in the elderly metastatic breast cancer patients in the United States Medicare population. Methods: A retrospective study was conducted among subjects aged ≥65 years and diagnosed with metastatic breast cancer between 1/1/00 and 12/31/05 using the SEER-Medicare linked database. For each subject, an index date was defined as the date of first observed metastatic breast cancer diagnosis. A subgroup of patients prescribed herceptin, a targeted therapy HER2+ve patients was identified. Survival rates (1-year and 5-year) were assessed. A Cox proportional hazards model was used to assess predictors of survival. Age, race, nodal status, hormone receptor status, Charlson Co-morbidity Index score and chemotherapy use were examined as covariates. Results: We identified 3,163 patients with metastatic breast cancer and an average follow up period of 29 months, of which 345 (10%) patients were prescribed herceptin. The 1-year and 5-year survival rates were 76% and 10% respectively with a mean survival of 2.4 years (median 2.1 years) in the overall population. Among patients prescribed herceptin (HER2+ve patients), the 1-year and 5-year survival rates were 85% and 6% respectively (mean 2.6 years). Among all patients, hormone receptor status double negative was associated with an increased risk of death {ER +ve/PR + ve [hazard ratio HR= 0.470; p<0.001], ER +ve/PR –ve [HR= 0.521; p<0.001] vs. ER-ve/PR-ve} as were a higher nodal involvement (>3 nodes) [HR = 1.557; p<0.0001 vs. 0 nodes] and higher Charlson Co-morbidity Index score [HR = 1.024; p<0.0001]. Age 65-74 [HR= 0.719; p<0.0001 vs. age > 85], age 75-84 [HR= 0.816; p<0.05 vs. age > 85] and chemotherapy use [HR] = 0.68; p<0.0001) were associated with a significant decrease in mortality risk. In the herceptin treated subgroup, ER-ve/PR+ve was associated with a significantly higher risk of death (HR= 3.396; p < 0.05) while ER+ve/PR-ve was associated with a lower risk of death ([HR] = 0.548; p <0.05) vs ER-ve/PR-ve. Conclusions: Hormonal status, greater nodal involvement, older age and increased co-morbidity burden were found to be significant predictors of death in elderly metastatic breast cancer patients.