Hormone Replacement Therapy - HRT and Cancer

Female Hormone Replacement Therapy (HRT) refers to commercially manufactured prescription pills, patches and creams containing estrogens and/or progestins to be used to replace the menopausal woman's decline in those hormones. HRT has been used for decades to relieve bothersome symptoms associated with menopause such as hot flashes and vaginal dryness. Even as the effectiveness of HRT was clear, many researchers and patients throughout the years have wondered about the effects of hormones on the risks of cancers, particularly cancers of the female reproductive organs, because of a possible sensitivity to hormones in those cancers. Generally, the prevailing thought until recent years had been that the overall risk of cancer as a result of HRT was very small. Women were reassured that unless they had certain personal risk factors, the available data did not support the idea of increased risk of cancers from HRT.

Results from a very large and thorough study, the Women's Health Initiative, along with other recent studies, have challenged the safety of HRT. It does appear that the incidence of three types of female cancers was increased in women who took HRT. Endometrial, ovarian and breast cancer risk appear to be increased by various types of HRT. The risk of colon cancer was found to be decreased in women who were taking HRT. Each cancer and its study results are discussed below.

Breast Cancer and HRT

Results from the Women's Health Initiative showed that the use of an estrogen/progesterone (combination) HRT increased the chances of developing breast cancer by 25%. This means that a woman taking HRT over the course of the study had a 25% greater chance of developing breast cancer. This translates to 8 additional cases of breast cancer per 10,000 women per year in the group taking combination HRT.