Anthracycline regimen adherence in older patients with early breast cancer

Background. Rates of anthracycline adherence in breast cancer (BC) patients are unknown, but noncompletion of chemotherapy is associated with worse outcomes. Methods. Using the Surveillance, Epidemiology, and End Results-Medicare database, we obtained demographics, comorbidities, tumor characteristics, and treatment and hospitalization data from stage I-III BC patients diagnosed at age >66 years in 1996-2005 treated with surgery who had anthracycline claims. We compared variables between patients with claims for less than four cycles, considered nonadherent cases, and those with claims for four or more cycles using logistic regression analyses. Results. The sample included 7,399 patients, of whom 1,222 (16.5%) were nonadherent cases. Two hundred forty-three (3.3%) patients had one claim, 298 (4.0%) had two claims, and 681 (9.2%) had three claims. The multivariate regression model showed statistically significant associations between nonadherence and older age, black race, unmarried status, diagnosis before the year 2001, and hospitalizations. Conclusions. Eighty-three percent of older patients with early-stage BC completed at least four cycles of an anthracycline-based chemotherapy regimen. We identified a subset of patients with a higher likelihood of not adhering to the course of treatment. Further research is warranted to develop interventions to enhance adherence.