Factors Associated with Low-Dose Tamoxifen Use among Women with Atypical Hyperplasia or Lobular or Ductal Carcinoma In Situ.

UNLABELLED: In 2019, professional guidelines incorporated low-dose tamoxifen as an option for breast cancer chemoprevention among women with atypical hyperplasia (AH) or lobular or ductal carcinoma in situ (LCIS/DCIS). We assessed factors associated with low-dose tamoxifen use among women diagnosed with AH, LCIS, or DCIS from 2016 to 2019 and from 2020 to 2023 compared with full-dose selective estrogen receptor modulators (SERM) or aromatase inhibitors (AI) at Columbia University Irving Medical Center in New York City. Uni- and multivariable logistic regression were used to calculate odds ratios (OR) and 95% confidence intervals (CI) for variables associated with low-dose tamoxifen use. Among 2,260 evaluable women, 834 (36.9%) initiated a SERM or AI, and 140 (6.2%) took low-dose tamoxifen. Comparing women diagnosed before or after 2019, chemoprevention uptake significantly increased (33.9% vs. 39.3%, P = 0.008), particularly low-dose tamoxifen (3.3% vs. 8.6%). Among women who initiated chemoprevention, diagnosis of high-risk breast lesions before age 50 (OR = 3.02; 95% CI, 1.99-4.58), diagnosis after 2019 (OR = 2.83; 95% CI, 1.81-4.41), AH/LCIS versus DCIS (OR = 2.90; 95% CI, 1.95-4.31), and medical oncology referral (OR = 1.61; 95% CI, 1.02-2.54) were significant predictors of low-dose tamoxifen use. Those who initiated low-dose tamoxifen as their first chemoprevention had the lowest 1-year discontinuation rate (24.3%) compared with full-dose SERMs/AIs (32.3%-37.9%, P = 0.027). Since 2019, we observed a significant increase in low-dose tamoxifen use and chemoprevention uptake overall. Among women who initiated chemoprevention, low-dose tamoxifen uptake was higher among younger women and those with less advanced breast lesions. Low-dose options of proven chemopreventive agents may increase acceptance of risk-reducing medications for breast cancer prevention.

PREVENTION RELEVANCE: This study provides evidence of increased use of low-dose tamoxifen in a prevention setting, particularly among younger women and those with less advanced breast lesions. Further research is needed to understand how to incorporate low-dose tamoxifen into patient-provider discussions to improve chemoprevention decision-making.