Abstract PS1-05-29: Patient-reported reasons for discontinuing adjuvant endocrine therapy: a survey of early-stage breast cancer survivors

Abstract Background: Adjuvant endocrine therapy (AET) for early-stage breast cancer (eBC) profoundlyreduces the risk of recurrence1, but the literature consistently reports high rates of discontinuation andnon-adherence2. This study aimed to identify the patient-reported reasons for discontinuing therapy. Methods: A self-administered, cross-sectional survey comprising open-ended questions wasconducted among female survivors of eBC who had been prescribed AET for a minimum of threemonths. Results: A total of 920 female survivors (median age 53 years) diagnosed with eBC were included inthe study. The median time since diagnosis was 2 years (IQR: 1.00-4.00), and 62% werepremenopausal at the time of their diagnosis. Among the 165 patients who discontinued or considered discontinuing AET without consulting theirphysician, the most frequently reported reasons were musculoskeletal pain (24.8%) and, as describedin responses to an open-ended question, unspecified severe adverse effects in general (18.8%). Thesewere followed by typical menopausal symptoms (15.5%), including hot flashes, night sweats, vaginaldryness, and osteoporosis and psychological effects (13.3%) such as depression, mood swings,memory problems, and irritability. In their open-ended responses, patients explained that despiteexperiencing significant adverse effects, they chose to continue AET, with fear of cancer recurrenceserving as the primary motivator. However, they also reported contemplating discontinuation due todiminished quality of life (QoL), emotional and cognitive challenges, and concerns about the long-term effects of the therapy. Discontinuations made in agreement with a physician (N=13) were primarily temporary and attributedto planned surgery (27.3%), switching AET (22.7%), gynaecological issues (20.4%), elevated liverenzymes (6.8%), or other adverse effects (22.7%). Conclusions: Although physicians rarely recommend discontinuing AET due to adverse effects, sucheffects remain the leading cause of patient-initiated treatment cessation. Effective side effectmanagement and personalised support are crucial for improving patients’ QoL and, in turn, promotingadherence to and persistence with AET. References: 1. Davies C, Pan H, Godwin J, Gray R, Arriagada R, Raina V, et al. Long-term effects ofcontinuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial. The Lancet 2013;381:805-16. https://doi.org/10.1016/S0140-6736(12)61963-1. 2. Yussof I, Mohd Tahir NA, Hatah E, Mohamed Shah N. Factors influencing five-yearadherence to adjuvant endocrine therapy in breast cancer patients: A systematic review. Breast2022; 62:22-35. https://doi.org/10.1016/j.breast.2022.01.012 Citation Format: A. Dugonjic Okrosa, T. Silovski, N. Dedic Plavetic, D. Kifer, A. Budisavljevic, H. Silovski, A. Seselja Perisin, R. Kelemenic Drazin, M. Skelin, L. Jajac Brucic, J. Jovic Zlatovic, I. Mucalo. Patient-reported reasons for discontinuing adjuvant endocrine therapy: a survey of early-stage breast cancer survivors [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-05-29.