Low Dose Tamoxifen for Breast Cancer Prevention: A Real-World Experience

Area of Science:

• Oncology
• Pharmacology

Background:

• Limited data exists on low dose tamoxifen (LDT) for breast cancer chemoprevention since its 2019 introduction.
• Assessing LDT uptake and associated factors is crucial for guiding clinical practice.

Purpose of the Study:

• To determine the rate of LDT uptake for chemoprevention at the institution.
• To identify patient and disease characteristics associated with LDT use.

Main Methods:

• Retrospective chart review of 477 women diagnosed with ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS), or atypical hyperplasia (2019-2021).
• Log-binomial models compared standard dose tamoxifen (SDT) vs. LDT use.
• Zero-inflated Poisson regression analyzed adverse event (AE) rates.

Main Results:

• 19% (N=89) of patients initiated LDT; 27% (N=129) initiated SDT; 20% (N=95) declined therapy.
• LDT use was higher in patients with LCIS or atypical hyperplasia (31.4%) compared to DCIS (17.4%).
• AE incidence rate was higher with SDT (1.9/1000 days) vs. LDT (1.3/1000 days), though overall AE frequency was not significantly different.

Conclusions:

• 19% of women with high-risk lesions initiated chemoprevention with LDT, with greater uptake in those with atypical lesions and/or LCIS.
• LDT is a viable option for chemoprevention in eligible women with high-risk lesions.
• Physicians should consider LDT for eligible women with high-risk lesions.