Combination Hormone Therapy Associated with Increase in Breast Density
Behind the Cancer Headlines®
January 7, 2003
A new study suggests that the use of combination hormone therapy, but
not estrogen alone, is associated with a modest increase in breast
density, a known risk factor for breast cancer. The findings appear
in the Journal of the National Cancer Institute.
The degree of breast cancer risk that is associated with breast density
is greater than that associated with almost all other known breast
cancer risk factors. A previous analysis of data from the
Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial, a
randomized trial looking at the effects of postmenopausal hormone
therapy (estrogen alone or estrogen plus three different progestin
regimens) on breast density, showed that some women who used
combination estrogen/progestin therapy experienced an increase in
breast density. However, the analysis did not look at the magnitude
of that increase. Past studies have suggested that the greater the
breast density, the greater the risk for breast cancer.
Gail A. Greendale, M.D., of the University of California Los Angeles
School of Medicine, and her colleagues examined digitized mammograms
at baseline and after one year of therapy from 571 postmenopausal
women enrolled in the PEPI trial who were randomly assigned to
receive daily doses of estrogen alone, estrogen plus cyclic
medroxyprogesterone acetate, estrogen plus continuous medroxyprogesterone
acetate, estrogen plus micronized progesterone, or a placebo.
They found that use of estrogen/progestin combination therapy, regardless of
how the progestin was given, was associated with 3% to 5% increases
in breast density. Use of estrogen alone was not associated with such
increases in breast density.
The authors conclude that the use of combination hormone therapy, but
not the use of estrogen alone, is associated with increases in breast
density. "However, the link between change in breast density
resulting from hormone use and change in breast cancer risk remains
uncertain," they say.
In an accompanying editorial, Rowan T. Chlebowski, M.D., Ph.D., of
the Harbor-UCLA Research and Education Institute in Torrance, Calif.,
and Anne McTiernan, M.D., Ph.D., of the Fred Hutchinson Cancer
Research Center in Seattle, point out that breast density is a useful
marker of increased risk for breast cancer, and they add that breast
density may be a valid marker of the effect of interventions that
increase or decrease breast cancer risk.
Journal of the National Cancer Institute, January 1, 2003