Breast cancer chemoprevention

What it is

Chemoprevention of cancer is set out by class of agent. The hormonal agents come first: the selective anti-estrogens tamoxifen and raloxifene reduce the risk of breast cancer; the aromatase inhibitors anastrozole and exemestane are the other anti-estrogen group; and the anti-androgens, the 5-alpha-reductase inhibitors finasteride and dutasteride, reduce the risk of prostate cancer.

Beside the hormonal agents three other groups are listed. Medication: aspirin and metformin. Vaccines: HBV to prevent HCC, and HPV to prevent cervical cancer. Diet related agents: retinoid and vitamin D to prevent breast cancer, folic acid to reduce SCC of head and neck, and calcium. Against breast cancer aspirin works mainly by suppressing platelets through inhibition of COX2.

How it is treated

For the woman who carries a pathogenic or a likely pathogenic variant in BRCA1 or BRCA2, the interventions that may be appropriate for risk reduction are written out as a whole set, not as a drug alone.

Increased surveillance for breast cancer: clinical examination starting at age 25, mammography starting at age 30, and MRI starting at age 25 to 29. Possible increased surveillance for gynecologic cancer with transvaginal ultrasound and CA-125. Risk-reducing bilateral mastectomy, by shared decision-making. A recommendation for risk-reducing bilateral salpingo-oophorectomy after childbearing, at age 35 to 40 for BRCA1 carriers and 40 to 45 for BRCA2 carriers, with discussion of the potential risks and benefits of hysterectomy. And preconception counseling.

Two points hold over the whole list. Pathogenic and likely pathogenic variants are treated the same for the purposes of surveillance and risk-reduction interventions, and these interventions are independent of family history.