A landmark study, backed by the American Cancer Society, may force a re-evaluation of the use of hormone replacement therapy (HRT), especially among the over 55s.
The study has confirmed earlier worries that artificial hormones can increase the risk of breast cancer, and the risk increases in the over 55s if they have been taking HRT for more than five years.
It has also established that combining estrogens with progestogens does not offer any protection against breast cancer, even though evidence suggests the combination can protect against endometrial cancer, normally caused by estrogens alone, the study says. The study is one of the first to evaluate the risks involved of using the combined hormones.
The study effectively endorses findings of early European studies, but commands special attention because of the sheer size of the study group and because it has been produced by Harvard Medical School, and backed bythe ACS.
They studied health reports from postmenopausal women in the Nurses Health Study, which represents 725,550 man years of follow-up; 1,935 cases of newly-diagnosed breast cancer were recorded.
Researchers discovered that the risk of breast cancer was significantly increased among women who were using estrogen alone, or estrogen plus progestogens, against those who had never taken HRT. Women who had been taking HRT for more than five years were at greater risk.
They also found that protection against osteoporosis diminished after women stopped taking HRT, even if they had been on the hormone for longer than seven years.
"Women over 55 years of age should carefully consider the risks and benefits of estrogen therapy, especially if they have used estrogen for five years or more," conclude the researchers.
"The significant increase in the risks of breast cancer and of death. . . suggests that the risks and benefits of hormone therapy among older women should be carefully assessed" which in the neutral tone of scientific papers amounts to a virtual damnation (NEJM, June 15, 1995).