Women in families with multiple cases of female breast +/- ovarian cancer are at increased risk of developing breast cancer. In the absence of a known germline pathogenic variant in a breast cancer predisposition gene, the exact levels of risk are difficult to determine. Risk models such as CanRisk, IBIS and iPrevent can calculate individual cancer risks.
Breast cancer risks can be low under age 40, even with family history, for women who do NOT carry a high-risk pathogenic variant. Potential harms of screening may outweigh benefits at this age, and an individual discussion is advised, based on the woman’s 10-year breast cancer risk assessment.
Bilateral risk reducing mastectomy reduces absolute breast cancer risk to <2%.
Mammography has been shown to reduce mortality for women at population risk of developing breast cancer. Annual mammography in an observational study of women aged 40-49 with a family history of risk of breast cancer (3% absolute risk during this time period) detected breast cancers at lower stages (smaller, fewer positive lymph nodes and lower grade) than in women who are not involved in a screening program.r
The sensitivity of mammography has been reported to be lower (50%) for women with high breast density, and limited evidence supports adding breast MRI, breast ultrasound or tomosynthesis to increase sensitivity. A systematic review of mammography with digital breast tomosynthesis use for breast cancer screening found lower false positive rates, recall rates and increased cancer detection when compared to standard 2D mammography, adding support for its use in screening.rr
Screening with use of MRI in addition to mammography has been shown to have a significant increase in sensitivity for women with a high risk of breast cancer based on family history (55% with mammography alone increasing to 98% with the addition of MRI). Cancers detected have also been earlier stage, required less adjuvant therapy and had a lower rate of metastatic disease.r However, false positive findings increased and specificity decreased with use of MRI.r
Five years of treatment with selective oestrogen receptor modulators (SERM), such as tamoxifen and raloxifene, or aromatase inhibitors (AIs), such as anastrozole or exemestane, have been shown to reduce the risk of oestrogen receptor-positive breast cancer in women identified to be at increased risk. A meta-analysis showed that tamoxifen reduced breast cancer incidence by 32% compared with placebo in women at increased risk. Tamoxifen was more effective at reducing breast cancer risk than raloxifene, but had greater toxicity. AIs (for post-menopausal women only) reduced breast cancer risk by 53% compared with placebo.r After cessation of therapy, persistent breast cancer risk reduction has been shown for tamoxifen and anastrazole.rr None of the medications have proven mortality benefit.