The most common type of HRT (hormone replacement therapy)—combined estrogen and progestogen—increases the risk of breast cancer by up to 80 percent, a new study has found.
The risk increases the longer that women take HRT—but it also falls off quickly once the therapy is stopped.
Researchers from the University of Nottingham say the risk is higher than an earlier study had estimated, although it varies between the different types of HRT and the length of time it’s taken. Comparing HRT usage in 98,611 women diagnosed with breast cancer and 457,498 healthy women, the researchers discovered there was a 15 percent increased risk in women taking estrogen-only therapy, and a 79 percent greater risk among those taking estrogen and progestogen.
But the risk virtually disappeared in women who had stopped taking estrogen therapy, although those taking the combined therapy still had a 16 percent raised risk, even years later.
The researchers emphasise that their study is observational and cannot prove that HRT definitely causes breast cancer.
(Source: BMJ, 2020; m3873; doi: 1136/bmj.m3873)
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