Adherence to Adjuvant Endocrine Therapy in Women With Breast Cancer: A Prospective Observational Study in Japanese Women

Abstract Introduction Nonadherence to adjuvant endocrine therapy has been poorly studied in Asian patients with breast cancer. We therefore assessed adherence to endocrine therapy among women with breast cancer in Japan. Patients and Methods We conducted a prospective observational study among Japanese women with hormone receptor-positive breast cancer. Patients brought their pill packets to visits for 1 year and answered a questionnaire. We also examined prescription records during the study period. Adherence to endocrine therapy was defined as patients who had taken > 80% of the pills according to the packets during the study. Clinicopathologic features and questionnaires were compared between adherent and nonadherent patients. Results A total of 234 patients completed the trial, of whom 85% demonstrated adherence based on pill packets, and 98% demonstrated adherence based on prescription records. Mastectomy, higher stage, nodal metastasis and adjuvant chemotherapy were correlated with adherence based on pill packets. Adjuvant chemotherapy was an independent factor associated with adherence. According to the questionnaire, adherent patients were more likely to consult a nurse when they had trouble with their medication. These patients also emphasized the efficacy rather than the side effects of the medication. Nonadherent patients were aware that they were being nonadherent. Conclusion The results of this study revealed that 85% of patients were adherent to endocrine therapy, but physicians were unaware of the nonadherent patients. Raised awareness of nonadherence and information sharing between patients and medical teams might increase adherence to endocrine therapy.