The value of high adherence to tamoxifen in women with breast cancer: a community-based cohort study

Background: Low adherence to adjuvant tamoxifen is associated with worse health outcomes but little is known about the cost-effectiveness of high adherence. Methods: We conducted an economic evaluation using data for all women with incident breast cancer between 1993 and 2000 who were subsequently prescribed tamoxifen in the Tayside region of Scotland. Patient-level, lifetime Markov models evaluated the impact of high vs low adherence to tamoxifen using linked prescribing, cancer registry, clinical cancer audit, hospital discharge and death records. Direct medical costs were estimated for each patient and quality-of-life weights were assigned. Recurrence information was collected by case note review and adherence calculated from prescribing records with low adherence classed below 80%. Results: A total of 354 (28%) patients had a recorded recurrence and 504 (39%) died. Four hundred and seventy-five (38%) patients had low adherence over the treatment period, which was associated with reduced time to recurrence of 52% ( P