Interruption and Non-Adherence to Long-Term Adjuvant Hormone Therapy Is Associated with Adverse Survival Outcome of Breast Cancer Women - An Asian Population-Based Study

This study aimed to evaluate the survival rate of women with breast cancer (BC) comparing persistence versus interruption and adherence versus non-adherence to adjuvant hormonal therapy (HT) in Asian population. Newly-diagnosed BC women from 2003 to 2010 were retrospectively identified from the Taiwan National Health Insurance Research Database. HT prescriptions were extracted to define treatment interruption and medication possession ratio. Their impacts on mortality were estimated by Cox regression with time dependent covariates. Interruption (HR: 1.32; 95% CI: 1.20, 1.46; P<0.0001) and non-adherence (HR: 1.45; 95% CI: 1.32, 1.59; P<0.0001) to adjuvant HT were significantly associated with increased mortality. Interruption to tamoxifen in younger patients and in patients receiving surgery (OP) with adjuvant chemotherapy (CT) was associated with increasing mortality rate when compared with their counterparts. Non-adherence to AIs in both younger and senior age groups and in OP with CT group also resulted in increasing risk. Treatment interruption and non-adherence to adjuvant HT were found to be associated with the increasing all-cause mortality of the Asian BC women; a greater impact of interruption and non-adherence on mortality was especially found in the younger BC population.