Hormone Replacement Therapy in Women with High Risk of Breast Cancer

Risks of HRT in High-Risk Women

Long-term use of HRT (≥20 years) of estrogen alone is associated with increased breast cancer risk (relative risk 1.42) 1
The U.S. Preventive Services Task Force (USPSTF) has concluded that there is fair to good evidence that HRT increases breast cancer incidence, with strongest evidence for combined estrogen-progestin therapy 2

For women at high risk of breast cancer, selective estrogen receptor modulators (SERMs) like tamoxifen or raloxifene could be considered as preventive strategies, depending on the woman's underlying risk for stroke and thromboembolic events 3, 4
Other effective interventions for preventing osteoporosis include weight-bearing exercise, bisphosphonates, and calcitonin 3, 4
Lifestyle modifications including regular physical activity, which has been associated with decreased breast cancer risk 1
Limiting alcohol consumption to less than one drink per day, as moderate alcohol intake (1-2 drinks/day) is associated with 30-50% increase in breast cancer incidence 1

The FDA has placed a black box warning on estrogen products indicating they should be prescribed at the lowest effective dose and for the shortest duration consistent with treatment goals 3, 5
The absolute increase in risk from HRT is modest but significant - per 10,000 women taking estrogen and progestin for 1 year, there might be 8 more invasive breast cancers, along with 7 additional CHD events, 8 more strokes, and 8 more pulmonary emboli 6