DOES USE OF ESTROGEN OR ESTROGEN-PROGESTIN HORMONES AFTER MENOPAUSE INCREASE THE RISK OF BREAST CANCER?
IT PROBABLY DOES, BUT THE INCREASED RISK IS MODEST.

(February 2003)

Many studies have been carried out on the dangers of taking hormones (hormone replacement therapy) after the menopause in regard to increased occurrence of breast cancer. The extent of the increased risk in various studies has ranged from none at all to about a doubled risk. A study from the well-respected Group Health Cooperative of Puget Sound in Seattle, Washington was reported in the February 13, 2002 issue of the Journal of the American Medical Association. They compared 705 post-menopausal women ages 50 to 74 years who developed breast cancer with 692 women of similar age who were cancer free. Those women using estrogens or estrogens plus progestin who were current users and who had been taking the hormones for at least five years had a 70 percent increased risk of developing breast cancer.

Commentary: This is a well-conducted study. It compares women with breast cancer and controls in regard to hormone use (a case-control study). That is not as good as giving a group of women hormones, having a control group given no hormones, and then following them for seven or ten years to determine who gets breast cancer. But, this is a useful study. It should be noted that a 70 percent increased risk sounds very large, but, in fact, in this kind of study, it is only a modest increase. Furthermore, some of the increased occurrence in hormone users may be related to the finding that those who had breast cancer detected also had more mammography tests.

Estrogen treatment of women postmenopausally has been severely attacked in recent studies, primarily for: (a) increasing risk of heart attack during the first few years of treatment, though it may actually protect women from heart attack thereafter (not yet proven) and (b) increasing the risk of breast cancer.

The evidence, taking all the studies together, does support the conclusion that there is a modest increase in risk of developing breast cancer among women taking hormone replacement (either estrogens alone or in combination with progestins).

But,

An article in the Archives of Surgery in September 2002 does offer an explanation for the finding that estrogen or estrogen-progestin treatment increases the occurrence of breast cancer, but does not increase death rates from breast cancer. The authors compared 144 postmenopausal women with breast cancer who used hormone replacement with an equal number of breast cancer cases in women who did not use hormones. The women in the hormone replacement group were more likely to have cancers detected only by mammography (very early cancer), the cancers were less aggressive looking, and the six-year survival rate was better. The investigators concluded "these effects of hormone replacement therapy seem to be due to development of less aggressive tumors rather than earlier detection".

Thus, it may well be that the increased risk of cancer is balanced by a lowered death rate because the tumors are less severe (less aggressive). This would account for the observation of an increased occurrence, but no increase in deaths. That is at least some good news for women who opt for estrogen or estrogen-progestin treatment postmenopausally.

Check, J., et al. The impact of hormone replacement therapy on the detection and stage of breast cancer. Archives of Surgery. Vol 137 (September) Pgs 1015-1021. 2002.

Risks and benefits of estrogen plus progestin in healthy postmenopausal women. Journal of the American Medical Association. Vol 288 (July 17) Pgs 321-333. 2002.

Chen, C.L., et al. Hormone replacement therapy in relation to breast cancer. Journal of the American Medical Association, Vol 287 (February 13) Pgs 734-741. 2002.