Abstract S5-03: Menopausal symptoms as predictors of long-term adherence in the International breast cancer intervention study (IBIS-1)

Tamoxifen reduces the risk of breast cancer among women at increased risk of the disease. The effectiveness of the drug is dependent on its appropriate use for the duration of therapy. Adherence for the full course of preventive therapy ranges from 60-80%. Early discontinuation is largely attributed to side-effects, but no studies have validated this using 5-year follow-up data. We assessed the role of menopausal side-effects on long-term adherence in the UK arm of the International Breast Cancer Intervention Study (IBIS-1). In the IBIS-1 trial, 4279 women in the UK were randomised to placebo vs. tamoxifen (20mg/day). A total of 292 were excluded (breast cancer, death, or other cancer), leaving 3987 to be included in the analysis (2000 placebo arm, 1987 tamoxifen arm). Adherence was calculated using data from six monthly clinical visits during the trial. Adherence ( Overall, 66.8% of women were adherent for at least 4.5 years (placebo: 71.5% vs. tamoxifen: 62.1%, p In the IBIS-I trial, we observed a significant effect of common menopausal symptoms on long-term adherence. These effects were largely similar between tamoxifen and placebo arms, suggesting women are attributing age-related menopausal symptoms to preventive therapy. To ensure women experience the full benefit of preventive therapy, interventions are required to support the management of menopausal symptoms and to promote adherence. The higher rate of drop-out in the early months of the trial suggests early intervention may be an effective way to promote long-term adherence. Citation Format: Smith SG, Sestak I, Forbes J, Howell A, Cuzick JJ. Menopausal symptoms as predictors of long-term adherence in the International breast cancer intervention study (IBIS-1) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S5-03.