Menopause Journal, July 2016

Many women and healthcare professionals continue to be concerned about the association of HRT use and breast cancer. Most recent evidence suggests that HRT does not cause breast cells to become cancerous, but that the use of combined HRT (estrogen and progestogen) for more than five years, may promote the growth of cancer cells which are already present in some women. Importantly, this means that the natural history of breast cancer is not affected by use of HRT.

Further reassuring evidence has been reported from Finland, studying 489,105 women using HRT in 1994 to 2009 and comparing breast cancer mortality rate with that in women not using HRT.

The study showed that the risk of dying from breast cancer was reduced in all users of HRT, regardless of duration of HRT use, age or whether the HRT was estrogen only or estrogen plus progestogen. For age, the largest reduction in risk was in the 50-59 age group, and for type of HRT, estrogen only users showed a larger risk reduction than estrogen plus progestogen.

Overall, in this Finnish population, 1 in 10 women with breast cancer will die from the disease, while 1 in 20 women with breast cancer who use HRT will do so.

While this is an observational study rather than a gold standard randomised controlled trial, these findings add more evidence to the understanding of association of breast cancer risk and of breast cancer mortality in women who use HRT.

Ref: Mikkola TS, Savolainen-Peltonen H, Tuomikoski P et al. Reduced risk of breast cancer mortality in women using postmenopausal hormone therapy: a Finnish nationwide comparative study. Menopause 2016 July 25