Breast Density, Cancer Link?
Study of Women 40 and Older Links Denser Breasts, Higher Breast Cancer Risk
Jan. 17, 2007 -- Among women 40 and older, denser breasts may mean greater
according to a new report.
In a review of studies looking at more than 2,200 Canadian women, those with
denser breasts were three to five times more likely to be diagnosed with breast
cancer during the study
The study appears in the January issue of The New England Journal of
"The time has come to acknowledge breast density as a major risk factor
for breast cancer," Karla Kerlikowske, MD, of the University of California,
San Francisco, writes in an editorial in the same issue.
The researchers included Norman Boyd, MD, of Canada's Ontario Cancer
Institute and the Campbell Family Institute for Breast Cancer Research.
The association between dense breasts and breast cancer isn't new; it dates
back to 1970, note Boyd's team and Kerlikowske.
The researchers suggest breast cancer risk assessment and screening
techniques such as digital mammography, ultrasound, and magnetic resonance
imaging (MRI) as possibly beneficial for women with denser breasts.
Breast Density Data
Boyd's team reviewed three studies on 1,112 Canadian women with breast
cancer and an equal number of women without breast cancer.
All of the women were 40-70 years old (average age: 56).
Each had gotten a mammogram every year or two for the previous eight
None was diagnosed with breast cancer based on the first of those
Based on the mammograms, women with extensive breast density were three to
five times more likely to be diagnosed with breast cancer during the study
Those results held when the researchers considered other breast cancer risk
Spotting Breast Cancers in Dense Breasts
It can be harder to spot tumors on mammograms of dense breasts. So it's
possible the tumors were masked by breast density on the first mammogram but
appeared on the later tests.
That's the most likely explanation, Boyd's team writes. If so, other imaging
techniques, including ultrasound, MRI, and digital mammography might help spot
such tumors early, note the researchers.
But they also point out another possibility -- that denser breasts might
harbor faster-growing tumors.
Younger women tend to have denser breasts than older women.
But it's not clear if the new findings apply to women under 40, since women
in that age range weren't included in the studies reviewed by Boyd's group.
Many factors -- including genetics and lifestyle -- can affect breast cancer
Early detection often improves survival.