A new analysis of a subset of the data from the 1990’s Women’s Health Initiative study looking into the effects of estrogen-progestin combination pills and estrogen-only therapies was published online in The Lancet Oncology today.
The study results need to be read with caution. The new analysis suggests that women who have had hysterectomies and use estrogen-only pills to relieve menopausal symptoms are about 20% less likely to develop breast cancer than those who didn’t take the hormone. The benefits lasted for at least five years.
Among the 7,600 postmenopausal women followed (all of whom had hysterectomies and were between ages 50-79) the group taking estrogen had 151 cases of breast cancer compared to 199 cases of breast cancer in the group taking placebos.
This is an intriguing analysis that needs further replication. Several components of this report suggest to BCAction that women proceed with caution:
- the results are inconsistent with the total body of evidence that links estrogen to higher risk of breast cancer and
- the original study from which this data was pulled wasn’t designed to look at breast cancer risk.
In addition, estrogen is a powerful hormone which plays a complex role in the body and is known to increase the risk of a number of other health problems besides breast cancer. Seductive as this study’s analysis may sound, our ongoing pursuit of protecting women’s health must always include a clear demonstration of benefits before encouraging women to take drugs that also have potential to cause harm. We will follow and report on any further research on this topic.