Effect of early discontinuation and nonadherence to adjuvant hormone therapy on mortality in women with breast cancer.

578 Background: Adjuvant hormonal therapy reduces mortality among women with hormone-sensitive breast cancer (BC). We investigated the effects of early discontinuation and nonadherence to hormonal therapy on mortality in women enrolled in Kaiser Permanente of Northern California. Methods: We identified women diagnosed with hormone-sensitive stage I-III BC, 1996-2006, and used automated pharmacy records to identify hormonal therapy prescriptions and dates of refill. We categorized patients as having discontinued therapy if 180 days elapsed from the prior prescription. Of those who continued therapy, we categorized patients as adherent if the number of pills dispensed from the date of the first prescription to the date of treatment completion covered ≥ 80%. We used Cox proportional hazards models to estimate the association between discontinuation and non-adherence with all-cause mortality controlling for socio-demographic and clinical variables. Results: Among 8,769 women, median age 62 (24-99), who filled...