Age-specific nonpersistence of endocrine therapy in postmenopausal patients diagnosed with hormone receptor-positive breast cancer: A TEAM study analysis

Background. Early discontinuation of adjuvant endocrine therapy may affect the outcome of treatment in breast cancer patients. The aim of this study was to assess age-specific persistence and age-specific survival outcome based on persistence status. Methods. Patients enrolled in the Tamoxifen Exemestane Adjuvant Multinational trial were included. Nonpersistence was defined as discontinuing the assigned endocrine treatment within 1 year of follow-up because of adverse events, intercurrent illness, patient refusal, or other reasons. Endpoints were the breast cancer-specific and overall survival times. Analyses were stratified by age at diagnosis (<65 years, 65-74 years, >75 years). Results. Overall, 3,142 postmenopausal breast cancer patients were included: 1,682 were aged <65 years, 951 were aged 65-74 years, and 509 were aged >75 years. Older age was associated with a higher proportion of nonpersistence within 1 year of follow-up. In patients aged<65 years, nonpersistent patients had lower breast cancer- specific and overall survival probabilities. In patients aged 65-74 years and patients aged >75 years, the survival times of persistent and nonpersistent patients were similar. Conclusion. Nonpersistence within 1 year of follow-up was associated with lower breast cancer-specific and overall survival probabilities in patients aged <65 years, but it was not associated with survival outcomes in patients aged 65-74 years or in patients aged>75 years. These results suggest that extrapolation of outcomes from a young to an elderly breast cancer population may be insufficient and urge age-specific breast cancer studies.