Systemic MHT in individuals with increased familial breast cancer risk

For individuals with high familial risk (3 times greater than the general population risk) of breast cancer (including those with mutations in genes such as BRCA1 or BRCA2), systemic MHT should only be started after specialist referral for individual assessment of risks and benefits. For some situations, for example, individuals with high familial breast cancer risk and early menopause or POI, the benefits of systemic MHT (to address estrogen deficiency) may outweigh the harms.

For individuals with a moderate increase in familial risk of breast cancer, systemic MHT may be used after an informed discussion of benefits and harms.

See the Cancer Australia website for advice on risk classification.

For a more personalised risk estimate, the iPrevent tool allows data on family history and other risk factors to be entered for an individual assessment to be used in discussion with a health professional. Although the extent to which MHT increases familial risk is not certain, the tool models this in its assessments.

Consider referral (eg to a cancer genetics service) for those at high risk, to obtain detailed risk assessment and management advice. Referral guidelines are available at the New South Wales Cancer Institute eviQ website.

No specific formulations or routes of estrogen are known to confer lower risk of breast cancer than others (for individuals at any level of risk). Cyclical combined MHT may be safer than continuous combined MHT. Limited data suggest risk may vary between progestogens; dydrogesterone and micronised progesterone may be safer than other progestogens, but no randomised controlled data are available to guide choice. Tibolone is considered to have similar breast risks to combined MHT. The long-term breast risks of conjugated estrogens+bazedoxifene are unknown.

Systemic MHT is contraindicated in individuals with a personal history of breast cancer, without specialist advice.