Women are recommended combination HRT in order to lessen the risk of oestrogen only regime but by giving a progestin (synthetic progesterone) as part of the regime it now seems it is not protective but can increase both risk and mortality rate for breast cancer. The alternative of giving bioidentical natural progesterone is not common, although it is known to protect women from increased risk of breast cancer and heart disease.

The news of this additional risk was published in The Journal of the National Cancer Institute in March 2013 and came as a result of information from the Women’s Health Initiative (WHI) in the USA. They found that in a randomized trial, estrogen plus progestin was associated with an increase in both breast cancer incidence and mortality.

Women At Risk

However this was a different result from previous studies, so researchers at Los Angeles Biomedical Research Institute looked at postmenopausal women with no prior hysterectomy, who had negative mammograms within two years and who were either users or non-users of estrogen and progestin combined therapy.

The results were clear: breast cancer incidence was higher in estrogen plus progestin users (combined HRT) than in nonusers.This also led the study authors to conclude that the higher breast cancer incidence of those using estrogen plus progestin may lead to increased breast cancer mortality and not just increased risk.

The National Cancer Institute, wrote that questions remain about whether the data analyzed from the WHI observational study resolves the differences in tumor prognosis and tumor characteristics when compared to the WHI randomized trial. They write that, “In general, tumors in estrogen plus progestin users in the WHI Observational Study were not significantly different from those in non-hormone users with regard to number of positive lymph nodes or tumor size, but were more likely to be well differentiated and positive for hormone receptors, findings which are similar to other observational studies.” This, however, did not translate into a survival benefit. They recommend further analyses in this and other datasets of currency and duration of hormone use in relationship to tumor development to fully resolve the issue of tumor characteristics associated with estrogen plus progestin therapy.

Decreasing the Risk

There are so many health risks associated with HRT, and also so many women find the side effects unmanageable, it is not surprising that so many abandon HRT within a year of starting it. Bioidentical HRT is available where natural progesterone and oestrogens are combined and knowing that progesterone (not the synthetic progestins) are actually protective of breast cancer and heart disease that it would seem to make sense that women are offered that option.