Duration and Toxicity of Adjuvant Trastuzumab in Older Patients With Early-Stage Breast Cancer: A Population-Based Study

Abstract

Few data are available regarding adjuvant trastuzumab use in older women with early-stage breast cancer. We examined rates and predictors of adjuvant trastuzumab completion and cardiac events in this population. We used Surveillance, Epidemiology, and End Results (SEER)-Medicare data to identify patients age ≥ 66 years with stage I to III breast cancer diagnosed between 2005 and 2009 who received trastuzumab. Completion of trastuzumab was defined as receipt of more than 270 days of therapy. We used multivariable logistic regression to examine patient, clinical, and geographic characteristics associated with trastuzumab completion. We also examined rates of hospital admissions for cardiac events. Among 2,028 women, most (71.2%) were younger than age 76 years and had a comorbidity score of 0 (66.8%); 85.2% received trastuzumab with chemotherapy. Overall, 1,656 women (81.7%) completed trastuzumab. Older patients and those with more comorbidity had lower odds of treatment completion (odds ratio [OR], 0.40 [95% CI, 0.30 to 0.55] for age ≥ 80 years v age 66 to 70 years; OR, 0.65 [95% CI, 0.49 to 0.88] for comorbidity score of 2 v 0). During treatment, 73 patients (3.6%) were hospitalized for cardiac events (2.6% of those who completed trastuzumab v 8.1% of those who did not; P < .001). Most older patients who initiated adjuvant trastuzumab completed therapy. Age and comorbidity were among factors that were associated with treatment completion, and rates of significant cardiac events were higher in those who did not complete therapy. Further exploration of toxicities and optimal treatments for older women with human epidermal growth factor receptor 2-positive breast cancer are warranted.