Estrogen HRT: No Breast Cancer Risk
No Added Breast Cancer Risk With Estrogen-Only Hormone Replacement Therapy After Hysterectomy
WebMD News Archive
April 11, 2006 -- After hysterectomy, estrogen-only hormone therapy does not
increase a woman's risk of breast cancer.
That's the word from the final analysis of the estrogen-only arm of the
Women's Health Initiative (WHI) study. The trial was stopped early because it
linked hormone therapy to increased risk of stroke, with no reduction in
The study had two arms. Menopausal women with an intact uterus received
estrogen plus progestin or an inactive placebo. That's because estrogen alone
increases a woman's risk of uterine cancer. Women who had undergone
hysterectomy, however, received estrogen-only hormone therapy or placebo.
The average five-year breast cancer risk estimates were similar between the
estrogen-plus-progestin group and the estrogen-only group.
Could this be true? Stanford researcher Marcia L. Stefanick, PhD, chairwoman
of the WHI steering committee, led a team that took a detailed look at the
estrogen-only data. Stefanick's report appears in the April 12 issue of The
Journal of the American Medical Association.
"The major finding is no increased risk of breast cancer in women taking
just estrogen," Stefanick tells WebMD. "There is a tendency for
decreased risk of breast cancer, but it is not statistically significant. This
means it would be inappropriate simply to say estrogen alone decreases breast
Stefanick says estrogen may be safer for some women than for others.
"Women at lower initial risk of breast cancer seem to be the ones who
have even lower risk if they go on estrogen," she says. "Women with a
higher risk of breast cancer seem to have even higher risk with
HRT Risk Overblown?
Stefanick says there are big differences between treating women who have had
a hysterectomy and women with an intact uterus. And there are big differences
between estrogen-only hormone therapy and estrogen-plus-progestin therapy.
"The media always talk about 'hormones do this' or 'hormones do
that,'" Stefanick says. "What we are clear on is estrogen plus
progestin does one thing in one group, and estrogen alone does something very
different in a different group. ... We cannot say it is all about progestin. But
we can say progestin plus estrogen gives a really different outcome than just
The study results are very reassuring to Hugh Taylor, MD, associate chief
for research in the obstetrics, gynecology, and reproductive sciences
department at Yale University. Taylor spoke at a news conference organized by
Wyeth, which makes Premarin and Prempro, the hormones tested in the WHI study.
Taylor has received speakers' fees from Wyeth, but has no financial interest in
the company. Wyeth is a WebMD sponsor.