By Suzanne Rostler
NEW YORK, Jan 28 (Reuters Health) -- Hormone replacement therapy (HRT),
taken by millions of women to relieve menopausal symptoms and lower the risk of
heart disease, may make it harder to pick up breast cancers on mammograms,
researchers report.
In women aged 50 to 69 who were taking HRT, mammograms picked up about 64%
of breast cancers in those who had the disease. In comparison, mammograms had an
accuracy of nearly 80% in women not taking the hormones, according to a report
in the January 22nd issue of The Lancet.
The study findings suggest that mammograms are just as accurate in women
under 50 who are taking hormones compared with those not on HRT.
"For women taking HRT, mammography is not as effective as for women not on
HRT," said study lead author Dr. Anne Kavanagh of the Cancer Epidemiology Centre
and the Anti-Cancer Council of Victoria in Australia, in an interview with
Reuters Health.
However, "breast cancer screening (mammography) is still the most
effective way of reducing their risk of dying from breast cancer," she added.
HRT causes an increase in the tissue density of the breast, according to
Kavanagh. This essentially mimics the greater density of breast tissue seen
naturally in younger women. This type of tissue appears white on a mammogram,
and could obscure signs of breast cancer, which also appear white on mammograms.
To arrive at their findings, the researchers measured the accuracy of
mammograms over a 2-year period in nearly 104,000 women from Victoria,
Australia.
The investigators found that mammograms were less accurate in HRT users
aged 50 to 69. However, in women under age 50 and those over age 69, the
accuracy of mammograms were the same regardless of whether or not they were
taking hormones.
The researchers also found that women who used HRT were more likely to
develop breast cancer after an initial mammography was negative than women who
did not use HRT.
"It may be possible to advise women to cease HRT for a brief period before
mammography," since any changes caused by the hormones may be reversible, the
authors suggest.
However, more research is needed to clarify which hormones and
combinations of hormones are most likely to lower sensitivity of mammography,
and how breast density contributes to mammography results.
"This information can then be used to advise women who use HRT about the
appropriate approach to screening," Kavanagh and colleagues conclude. "Women
should also be given information about the relation between the accuracy of
mammographic screening and HRT use when they are making decisions about whether
to start HRT."
