Use and Outcomes of Adjuvant Chemotherapy in Older Women With Breast Cancer

Abstract

Purpose This study was undertaken to determine patterns and outcomes of adjuvant chemotherapy use in a population-based cohort of older women with primary breast cancer. Patients and Methods Women were identified from the Surveillance, Epidemiology, and End Results–Medicare-linked database who met the following criteria: age ≥ 65 years, stage I to III breast cancer, and diagnosis between 1991 and 1999. Adjuvant chemotherapy use was ascertained by Common Procedural Terminology J codes. Logistic regression analysis was performed to determine factors associated with chemotherapy use. Multivariate Cox proportional hazards models were used to calculate the hazard of death for women with and without chemotherapy. Results A total of 41,390 women met study criteria, of whom 4,500 (10.9%) received chemotherapy. The use of adjuvant chemotherapy more than doubled during the 1990s, from 7.4% in 1991 to 16.3% in 1999 (P < .0001), with a significant shift toward anthracycline use. Women who were younger, white, with lower comorbidity scores, more advanced stage disease, and estrogen receptor (ER) –negative disease were significantly more likely to receive chemotherapy. Chemotherapy was not associated with improved survival among women with lymph node–negative (LN) disease or LN-positive, ER-positive disease (hazard ratio [HR], 1.05; 95% CI, 0.85 to 1.31). However, among women with LN-positive, ER-negative breast cancer, chemotherapy was associated with a significant reduction in breast cancer mortality (HR, 0.72; 95% CI, 0.54 to 0.96). A similar significant benefit of chemotherapy was seen in the subset of women age 70 years or older (HR, 0.74; 95% CI, 0.56 to 0.97). Conclusion In this observational cohort, chemotherapy was associated with a significant reduction in mortality among older women with ER-negative, LN-positive breast cancer.