At the beginning of 2015, a review of 52 epidemiological studies showed a statistically significant risk of ovarian cancer in women exposed to menopausal hormone therapy.

There appeared to be a higher risk, including in women exposed for less than 5 years. The results were comparable in European and North-American studies, even though the most common hormone replacement therapies are different. They were also similar whether the replacement hormones were oestrogen alone or a combination of oestrogen and progestin.

This review does not include comparative data for the different hormone therapies, but it is probable that the risk of cancer is increased with all substances having oestrogenic effects, including tibolone.

Some studies showed that the risk was reduced over time once the exposure stopped, but that there was still a statistically significant risk 10 years after halting hormone replacement therapy. The excess risk appears to be in the order of 1 ovarian cancer per 1000 women exposed to menopausal hormone therapy for 5 years around the age of 50. And given the mortality associated with this cancer in the general population, the excess mortality is estimated at 1 death per 1700 women exposed.

In practice, the harm-benefit balance of hormone replacement therapy is unfavourable due to the cardiac harms and the risk of cancer. If it is decided to proceed with hormone replacement therapy despite the risks, it is advisable to review the decision regularly with the patient, and to use the lowest dose for the shortest possible time.

©Prescrire 1 January 2016

"Postmenopausal hormone replacement therapy: ovarian cancer" Prescrire Int 2016; 25 (167): 16. (Pdf, subscribers only).