A new analysis of data from the Women’s Health Initiative now casts doubt on previous researcher’s findings that taking hormone replacement therapy (HRT) isn’t dangerous. The study, published Friday by the Journal of the National Cancer Institute, concludes that the prognosis for cancers related to hormone replacement therapy is just as dire as for other breast cancers. As a result, women who turn to the treatment are more likely to die of breast cancer than their non-hormone-taking peers.
The principal investigator for the Women’s Health Initiative and lead author of the new study stated, “You could fill a basketball arena with the women who get the disease.” “It seems like you’d want to reach a higher threshold before you take it.”
Nearly 70,000 postmenopausal women participated in randomized clinical trials as part of the Women’s Health Initiative project. The study participants who took estrogen plus progestin had higher rates of breast cancer diagnoses and of breast cancer deaths.
At the same time, more than 90,000 additional women took part in a related observational study that tracked details about their health and hormone use over an average of 11 years. Along with other observational studies, this one found that women who took hormones to treat menopause symptoms and got breast cancer were less likely to die from the illness than women who got breast cancer without taking hormones.
So he and his team identified a subset of more than 41,000 women from the observational study who more closely matched the women who took part in the randomized trial. In doing so, the researchers set aside data on women who were not using hormones when they participated in a study but had taken them in the past — a factor that had the potential to complicate the findings.
The new results fell more closely in line with the findings from the original randomized trial: Survival after breast cancer was similar for both hormone users and non-users. Tumors that arose in women who took hormones were no less deadly.
They had appeared to be, however, because women who had taken hormones years before might have already developed aggressive cancers and would not have been able to participate in the study in the first place.