Adherence to Endocrine Prevention in Patients with Atypical Hyperplasia and Lobular Carcinoma In Situ: Promising Trends from Real-World Use of Low-Dose Tamoxifen.

[BACKGROUND] Endocrine prevention is a well-established preventative strategy for women with high-risk lesions (HRL). The objective of the study was to evaluate factors associated with endocrine prevention adherence in this patient population.

[PATIENTS AND METHODS] We performed a retrospective cohort study of all women referred for atypical ductal and lobular hyperplasia (ADH/ALH) and lobular carcinoma in situ (LCIS) between 2019 and 2025. Data pertaining to eligibility, initiation, and adherence to endocrine prevention were extracted with univariate analyses performed to evaluate factors associated with adherence.

[RESULTS] Among 200 female patients with HRL, 112 (56%) had ADH, 72 (36%) had ALH, and 16 (8%) had classical LCIS. The median age was 55 years (IQR 50-62 years), with 126 (63%) patients accepting a prescription for endocrine prevention. Low-dose tamoxifen was the most common regimen prescribed (65.1%), compared with regular-dose tamoxifen (13.5%), raloxifene (16.7%), and aromatase inhibitors (4.8%). At a median follow-up of 37 months (IQR 18-49 months), 83 of 126 women (65.9%) initiated endocrine prevention and 72 (57.1%) remained adherent. Age (67.7% 51-60 years versus 47.1% < 50 years, p = 0.046), family history of breast cancer (71.0% vs. 52.6%, p = 0.048), and awareness of endocrine prevention (75.0% vs. 52.0%, p = 0.03) were significantly associated with adherence. Of 50 patients who initiated tamoxifen 5 mg, 46 (92%) remained adherent, and of 13 women who completed at least 3 years of therapy, 9 (69.2%) elected to complete a total 5 year course of low-dose tamoxifen.

[CONCLUSIONS] Adherence to endocrine prevention is high in women who initiate medication, with few discontinuing due to side effects.