Menopause Hormone Therapy: 'Safe' Time?
New Studies Probe Timing of Hormone Replacement Therapy and Breast Cancer Risk
First Two Years: 'Safe' or Not?
Calle's team looked at breast cancer risk in more than 67,000 postmenopausal women, including those taking estrogen only or estrogen-plus-progestin for at least a year or not taking any hormone therapy. The data came from an observational study; the women weren't assigned to any particular treatment plan.
The researchers identified a possible window of two to three years in which there was no sign of increased breast cancer risk in women taking estrogen plus progestin.
"In terms of our data, it looks pretty safe; there is absolutely no increased risk," Calle tells WebMD. But she cautions that that finding of a possible "safe" period "needs to be replicated in other studies ... the numbers are small in our study."
Stefanick and Chlebowski point out that taking hormone therapy can increase breast density, making it harder to spot breast cancers. "Do we have evidence that there really are fewer cancers or are we seeing that it's harder to detect them?" Stefanick asks. "If you have something that interferes with diagnosis, you're going to have a really hard conceptual time defining a completely safe interval," says Chlebowski.
Asked about that, Calle says that "theoretically, it could be that screening is not as effective in picking up these tumors" because of increased breast density while women are taking hormones. "We can't directly study that," says Calle, explaining that her team didn't have the women's mammograms to review. Calle says that Stefanick and Chlebowski's hypothesis is "not unreasonable," but that "there's not really a way to test it or to refute it" with the data she used.
The breast density issue "is something they could look at in a future study," says breast cancer specialist Jennifer Litton, MD, an assistant professor of medicine at the University of Texas M.D. Anderson Cancer Center. Litton wasn't involved in either study.