Abstract PS07-04: Improved uptake and adherence to prevention medication with use of baby tamoxifen in patients at high risk for breast cancer

Abstract Background: Women at increased risk for breast cancer (BC) may benefit from taking prevention medication (PM) with tamoxifen (tam). Historical uptake to PMs for women who qualify has been low. Recent studies have shown baby tam (5mg/day) to have similar efficacy to standard dosing (20mg/day) with lower risk for adverse events (AEs) in women with DCIS or high risk intraepithelial lesions. Herein, we aimed to evaluate uptake, adherence, and tolerability of baby tam in women at increased risk for BC and those with DCIS. Methods: Women seen at the Mayo Clinic Breast Center in Minnesota or Florida who qualified for PM due to DCIS, high risk intraepithelial lesions (IELs) including LCIS and/or AH, or with increased risk based on validated BRCAT or IBIS model calculation (BCRAT 5 year risk ≥ 3% or IBIS 10 year risk ≥ 8%) were offered participation. All women received consultation with a breast specialist for discussion of PM rationale, benefits, side effects, and risks. Patients received baseline survey to assess understanding of their risk and role for PM and then 1 year follow-up survey to assess adherence and tolerability. Results: 41 patients consented for participation and 31 of those completed follow-up at 1 year.Median age of enrollment was 49 years. After initial consultation, 90% (n=37) reported good or complete understanding of BC risk. Of the 31 patients included in 1 year follow-up, 5 patients had DCIS, 13 had high-risk IELs, and 13 qualified based on BCRAT/IBIS calculation. Seventy-four percent (n= 23) of patients reported they took baby tam after consultation. No differences in age (p=0.89), education (p=0.13), or menopause status (p=0.11) between those who did and did not take medication were seen. Those who initiated baby tam were more likely to have DCIS or high risk IEL compared to those who did not (p 0.001). Seventy-eight percent (n=18) of those who initiated baby tam were still taking medication at 1 year follow-up. Of patients who discontinued baby tam, all cited side effects as primary reason for discontinuation, with hot flashes (n=2), night sweats (n=2), and fatigue (n=2) being most common. Patients who continued medication had higher estimated BC risk compared to those who discontinued baby tam (IBIS 10 yr risk 12.7% vs 7.6%, p = 0.027). Patients with DCIS or high risk IEL were more likely to continue medication at 1 year compared to those patients who qualified for PM based on calculated BCRAT/IBIS score (p=0.05). Only 1 patient with DCIS and 1 patient with high-risk IEL discontinued baby tam at 1 year. Conclusions: Uptake to baby tam after informed discussion in patients who qualify is high, especially in those patients with high risk IELs or DCIS. Adherence and tolerability at 1 year follow-up is improved compared with traditional dosing of tam. Qualifying criteria for patients who did and did not take baby tamoxifen after informed consultation with breast specialist Citation Format: Lauren Cornell, Sandhya Pruthi, Karthik Ghosh, Klassen Christine, Pooja Advani. Improved uptake and adherence to prevention medication with use of baby tamoxifen in patients at high risk for breast cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS07-04.