Abstract PS3-09-07: Adherence to adjuvant endocrine treatment in women 36-56yrs with a hormone receptor-positive breast cancer: Patient compliance and impact on prognosis

Abstract Background Adjuvant endocrine therapy (AET) is essential in treating early hormone receptor-positive (HR+) breast cancer, significantly reducing recurrence and mortality. However, side effects often lead to poor adherence, with discontinuation rates up to 50% within five years. This study assessed adherence rate (AR) and the impact of AET compliance on prognosis in women aged 36-56 treated at UZ Leuven. Methods This retrospective cross-sectional study analyzed AET adherence in all high-risk early HR+ breast cancer patients diagnosed at UZ Leuven between 01/01/2008 and 31/12/2018 and who received chemotherapy. Data were obtained from clinical records and pharmacy dispensing information from public and hospital pharmacies, provided by Belgian health insurance. AR was measured by medication possession ratio (MPR), defined as the number of pills dispensed per year divided by 365.25 days. Non-adherence and poor adherence were defined as MPR