Estrogen-only menopausal hormone therapy and the reduced incidence of breast cancer

The recent report from the San Antonio Breast Cancer Symposium1 that unopposed conjugated estrogen (“estrogen only”2) use in postmenopausal women reduced the incidence of breast cancer is important. These data put the role of estrogen in breast cancer into perspective for both physicians and women. The data, which are based on a reanalysis of the Women’s Health Initiative (WHI), indicate that there is a subset of women who have previously had a hysterectomy who do not have an increased risk or incidence of breast cancer while using conjugated estrogens for menopausal symptoms. The position of the International Menopause Society is that counseling and the decision regarding the use of any hormone therapy be based on an individual risk–benefit assessment of the woman by her physician. This is an important qualifier, because hormone therapy can have positive effects on menopausal symptoms and quality of life in many postmenopausal women. Previous publications from the WHI have indicated an increased incidence of breast cancer in women with an intact uterus who used both estrogen and a progestin therapy. The current data indicate that there are women who could use estrogen therapy without increasing their risk of breast cancer.

Risk factors and the incidence of breast cancer are important in the understanding of who can or cannot use hormone therapy. Risk factors are used by physicians to determine the use of many medications. The risk–benefit ratio for women who are candidates for hormone therapy is just one of these. Risk factors for breast cancer are well known and include a history of breast cancer in a first-degree or second degree relative (mother or sister, paternal aunt or grand mother) especially with evidence of BRCA-1/2 mutations, increased breast density at mammograms, previous biopsy with atypical hyperplasia, thoracic radiotherapy, obesity, alcohol and physical inactivity. Factors that reduce the woman’s risk of breast cancer are considered in these discussions; an early age of first full term pregnancy, long term breast feeding, exercise and no history of fibrocystic breast disease are associated with a reduced risk of breast cancer. Physicians take these findings into account when prescribing or considering hormone therapy in postmenopausal women. There are women who do not have breast cancer risk factors and who do not increase their risk of breast cancer while using unopposed oral estrogen therapy. The recent reanalysis of the WHI data is reassuring to both women and physicians that women at low risk for breast cancer do not increase the incidence of breast cancer while using conjugated estrogen-only therapy.

The International Menopause Society urges all postmenopausal women to have annual physical examinations, use preventive health techniques such as monthly breast self-examination, utilize mammograms for screening, and have a discussion with their physician of their individual risks and benefits related to breast cancer and hormone therapy.

Commenting for the International Menopause Society, Professor David F. Archer MD (Norfolk, VA, USA) said:
“The reanalysis of the WHI data is reassuring to both women and physicians that women at low risk for breast cancer do not increase the incidence of breast cancer while using conjugated estrogens-only therapy. This finding supports the position of the International Menopause Society that any decision on the use of hormone therapy be based on an assessment of individual risks and benefits. These are different for each woman, and so the decision on hormone use should be taken after evaluating the risks and benefits, and subsequent discussions between a woman and her physician.”