THURSDAY, Oct. 7 (HealthDay News) -- Women with an early form of
breast cancer who have dense breasts may be at higher risk of
getting a second breast cancer, particularly in the opposite
breast, a new study indicates.
"The risk appears to be stronger for the opposite breast than for the breast that originally had the cancer," said Laurel A. Habel, a research scientist at Kaiser Permanente's Division of Research in Oakland, Calif.
Habel is lead author of the study published Oct. 7 in
Cancer Epidemiology, Biomarkers & Prevention.
Women with the most dense breasts, as seen on mammograms, "were
at about twice the risk of a second cancer, and the risk was closer
to threefold for the opposite breast," Habel said.
Dense breast tissue is made up mostly of ductal structures and
connective tissue, while non-dense breast tissue is mostly fatty,
Habel said. On a mammogram, dense tissue appears white; non-dense
looks dark gray.
Experts can't say for sure why density is linked with cancer
risk, Habel said, but these findings echo the results of previous
studies. In 2004, Habel's team reported a link between denser
breasts and a higher risk of second breast cancers among women with
ductal carcinoma in situ (DCIS), very early breast cancer, who were
enrolled in a clinical trial.
Other research, published in 2007, found that DCIS patients with
higher breast density were at increased risk of a second cancer in
the opposite breast.
In the most recent study, conducted from 1990 to 1997, Habel's
team followed 935 women diagnosed with early-stage breast cancer
(DCIS) who underwent breast-conserving surgery. The follow-up was
for a median of more than eight years. During that time, 164 (18
percent), had a second cancer in the same breast, and 59 (6
percent) had a new cancer in the opposite breast.
Habel said she can't explain the higher risk for the opposite
breast. "What we do see is, the amount of density is quite similar
in both breasts," she said.
Previous research has established breast density, which is
influenced by genetic factors, as a strong risk factor for getting
breast cancer, although Habel said she suspects many women are
still not aware of it as a risk factor.
Women aren't routinely told if their mammogram reveals dense
breasts, although doctors may mention extreme density, she
"It's good to know if they're dense," said Dr. Joanne Mortimer, director of women's cancer programs at the City of Hope Comprehensive Cancer Center in Duarte, Calif.. A women can ask her doctor, she said.
Breast density declines with age, and obese women have denser
breasts than leaner women, Mortimer said.
The new study, she said, confirms earlier research. The
practical aspect may be to help women make treatment decisions, she
For instance, some women diagnosed with breast cancer choose to
undergo a mastectomy on the unaffected breast as a preventive
measure. "People do it for emotional reasons," she said.
The new research suggests that breast density may be a factor to
consider when debating treatment options, "but not as a single
factor," Mortimer said. More study is needed on the density-cancer
link before it's relied on strongly in decision-making, she
To learn more about breast cancer recurrence, visit
Johns Hopkins Medicine.
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