Tamoxifen for Breast Cancer Chemoprophylaxis

Patient Selection Criteria

The American Society of Clinical Oncology recommends tamoxifen as a chemoprevention option for women aged 35 years or older with a 5-year projected absolute breast cancer risk ≥1.66% according to the NCI Breast Cancer Risk Assessment Tool, or with lobular carcinoma in situ (LCIS) 1, 2
Tamoxifen specifically reduces the risk of estrogen receptor (ER)-positive breast cancers but does not prevent ER-negative breast cancers 3
Risk factors that should prompt consideration of tamoxifen chemoprophylaxis include age ≥35 years with family history of breast cancer 1, 2
History of atypical ductal hyperplasia should prompt consideration of tamoxifen chemoprophylaxis, as recommended by the National Comprehensive Cancer Network 4, 5
History of LCIS should prompt consideration of tamoxifen chemoprophylaxis, as recommended by the National Comprehensive Cancer Network 1, 6

The NCI Breast Cancer Risk Assessment Tool (Gail model) should be used to identify women with a 5-year risk ≥1.66% 7, 5
Risk should be calculated periodically as a woman's risk increases throughout her lifetime, as recommended by the American Society of Clinical Oncology 3
The risk-benefit ratio is most favorable for women with higher breast cancer risk and lower risk of adverse effects, as reported by the American College of Physicians 7, 5

Tamoxifen is contraindicated in women with a history of deep vein thrombosis or pulmonary embolism, as recommended by the American Society of Clinical Oncology 1, 2
Tamoxifen is contraindicated in women with a history of stroke or transient ischemic attack, as recommended by the American Society of Clinical Oncology 1, 2
Tamoxifen is contraindicated during prolonged immobilization, as recommended by the American Society of Clinical Oncology 1
Tamoxifen is contraindicated in pregnancy or women who may become pregnant, as recommended by the American Society of Clinical Oncology 1, 2
Tamoxifen is contraindicated in nursing mothers, as recommended by the American Society of Clinical Oncology 1

The balance of benefits and harms is most favorable for women in their 40s at increased breast cancer risk without predisposition to thromboembolic events, as reported by the American College of Physicians 7, 8
The balance of benefits and harms is most favorable for women in their 50s at increased breast cancer risk without predisposition to thromboembolic events and without a uterus, as reported by the American College of Physicians 7, 8
Women with a personal history of atypical hyperplasia or LCIS are optimal candidates for tamoxifen chemoprophylaxis, as recommended by the National Comprehensive Cancer Network 4, 6

The risk reduction benefit of tamoxifen continues for at least 10 years after the 5-year treatment period, as reported by the American Society of Clinical Oncology 1, 2

Tamoxifen increases the risk of endometrial cancer, particularly in women over 50 years, as reported by the National Comprehensive Cancer Network 4
Tamoxifen increases the risk of thromboembolic events (deep vein thrombosis, pulmonary embolism), as reported by the National Comprehensive Cancer Network and the American College of Physicians 4, 7

Failing to reassess breast cancer risk periodically as risk increases with age is a common pitfall to avoid, as recommended by the American Society of Clinical Oncology 3
Recommending tamoxifen to women over 60 years without careful consideration of thromboembolic risk is a common pitfall to avoid, as reported by the American College of Physicians 7, 8
Not discussing the specific benefits and risks with each patient based on her individual risk factors is a common pitfall to avoid, as reported by the American College of Physicians 7, 5
Overlooking the long-term protective effect that continues after the 5-year treatment period is a common pitfall to avoid, as reported by the American Society of Clinical Oncology 1, 2