When, how long and type of hormone therapy affects breast cancer risk

CANCER DIGEST – Aug. 30, 2019 – A new analysis of data linking menopausal hormone therapy and breast cancer incidence shows that when and how long and the type of hormone therapy makes a difference.

Using data from more than 100,000 women with breast cancer from 58 epidemiological studies worldwide, researchers found that:

• Starting at age 50 years, would increase breast cancer incidence from age 50 to 69 years by about one additional case in every 50 users of oestrogen plus daily progestogen
• One in every 70 users of oestrogen plus intermittent progestogen
• One in every 200 users of oestrogen-only menopausal hormone therapy (MHT)

The findings suggest that all types of MHT, except topical vaginal estrogens, are linked to increases in risk of breast cancer, and the risks are greater for users of both estrogen and daily progestogen therapy compared to estrogen-only therapy and estrogen with intermittent progestogen regimens. The study appears in the Aug. 29, 2019 The Lancet.

The researchers also found that the excess risk appears to persist for more than 10 years after stopping MHT and the longer the MHT, the longer the risk persisted.

A previous analysis of worldwide data found the increased risk of breast cancer associated with MHT, but there wasn’t enough data in that study to look at the differences in risk among the different types of MHT.

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