Evidence Lacking for HRT-Breast Cancer Link
Researchers took fresh look at three large studies, concluded data wasn't convincing
By Kathleen Doheny
THURSDAY, March 14 ( HealthDay News) -- Although several large studies in recent years have linked the use of hormone therapy after menopause with an increased risk of breast cancer, the authors of a new analysis claim the evidence is too limited to confirm the connection.
Dr. Samuel Shapiro, of the University of Cape Town Medical School in South Africa, and his colleagues took another look at three large studies that investigated hormone therapy and its possible health risks -- the Collaborative Reanalysis, the Women's Health Initiative (WHI) and the Million Women Study.
Together, the results of these studies found overall an increased risk of breast cancer among women who used the combination form of hormone therapy with both estrogen and progesterone. Women who have had a hysterectomy and use estrogen-only therapy also have an increased risk, two of the studies found. The WHI, however, found that estrogen-only therapy may not increase breast cancer risk and may actually decrease it, although that has not been confirmed in other research.
After the WHI study was published in July 2002, women dropped hormone therapy in droves. Many experts pointed to that decline in hormone therapy use as the reason breast cancer rates were declining.
Not so, Shapiro said: "The decline in breast cancer incidence started three years before the fall in HRT use commenced, lasted for only one year after the HRT drop commenced, and then stopped."
For instance, he said, between 2002 and 2003, when large numbers of women were still using hormone therapy, the number of new breast cancer cases fell by nearly 7 percent.
In taking a look at the three studies again, Shapiro and his team reviewed whether the evidence satisfied criteria important to researchers, such as the strength of an association, taking into account other factors that could influence risk. Their conclusion: The evidence is not strong enough to say definitively that hormone therapy causes breast cancer.
The study is published in the current issue of the Journal of Family Planning and Reproductive Health Care.