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 Breast density increases breast cancer risk and can mask tumors
during mammograms, the researchers explain in the Annals of Internal
Medicine.
In some states, healthcare providers must tell women if they have
dense breasts. Those women sometimes then go on to have additional
screenings, such as ultrasound scans or magnetic resonance imaging (MRIs).
But in the new study, the researchers found that not all women with
dense breasts have a high enough risk for breast cancer after a
normal mammogram to justify having more screening tests.
Instead, they found that two specific groups of women with dense
breasts were likely to benefit from extra screening, taking into
account their risk for breast cancer in the next five years as
calculated using an online tool called the Breast Cancer
Surveillance Consortium (BCSC) score (http://bit.ly/1PuxYZF).
The first group consists of women with extremely dense breasts and a
BCSC-calculated five-year breast cancer risk of 1.67 percent or
greater.
The second group consists of women with heterogeneously dense
breasts and a BCSC-calculated five-year risk of 2.50 percent or
greater.
Women in these specific groups, which represent about a quarter of
women with dense breasts, should discuss whether extra screening may
be appropriate in addition to a mammogram every two years as
recommended for women are 50 to 74, the authors write.
"Our paper helps women in that it really identifies people for whom
screening is most important," said lead author Dr. Karla Kerlikowske
of the San Francisco Veterans Affairs Medical Center. "Some don’t
have to be concerned."
While those additional tests may help in finding tumors, the
researchers warn they may increase the risk of so-called
false-positives, which may lead to biopsies.
For the new study, researchers analyzed data from more than 300,000
women age 40 to 74 with no history of breast cancer or breast
implants. The women received digital mammograms between 2002 and
2011, when their breast density was recorded.
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The researchers also calculated each woman’s five-year breast cancer
risk using the BCSC online tool, which takes into account age, race,
family history of breast cancer, breast density, and whether or not
a woman has had a breast biopsy in the past.
Available evidence suggests that women with dense breasts may be 1.2
to 2 times more likely to be diagnosed with cancer than those with
average density, but since up to half of women have dense breasts,
it is difficult to call density a “risk factor” for cancer,
according to Dr. Nancy Dolan of Northwestern University Feinberg
School of Medicine in Chicago, who coauthored an editorial
accompanying the new study.
In the U.S. currently, most women who do not have a high lifetime
risk of cancer would have to pay out of pocket for an MRI in
addition to their recommended mammograms, which likely limits
widespread use, Dolan told Reuters by email.
“Supplemental screening increases the rates of biopsy, cost and
patient anxiety,” Dolan said. “Even among (women with) above average
risk, supplemental screening with ultrasound has a very high false
positive rate compared to mammography.”
The new study provides compelling evidence that breast density
should not be the sole criteria to guide decisions about supplement
screening, she said.
SOURCE: http://bit.ly/SQRXAa Annals of Internal Medicine, online May
18, 2015.
(Corrects name of researcher in paragraph 9 from Kurlikowske to
Kerlikowske.)
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