Currently it is suggested that all women with dense breasts get ultrasounds or other extra screenings after a mammogram, but a new study is now suggesting that those added tests may actually benefit only certain women.

Breast density increases the risk of breast cancer and can actually mask tumors during mammograms, explained researchers in the Annals of Internal Medicine.  In some states, healthcare providers must tell women if they do have dense breasts.  Those women then often go on to have additional screenings including ultrasound scans or magnetic resonance imaging (MRI).

However, in the new study researchers found that not all women with dense breasts have a high enough risk for breast cancer after a normal mammogram to justify having those extra screening tests.

Instead, researchers found two specific groups of women with dense breasts were likely to benefit from the extra screening procedures, taking into account their risk for breast cancer in the next five years as calculated using a tool called the Breast Cancer Surveillance Consortium score.

The first group is made up 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 BCBS calculated five-year risk of 2.5 percent or greater.

The women in these two groups represent about a quarter of women with dense breasts and should discuss whether extra screening may be appropriate in addition to the traditional mammogram every two years as recommended for women age 50 to 74, the authors said.

"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 the additional tests may help find tumors, the researchers also warned that it could increase the risk of false positives, which may lead to biopsies.

For the study, researchers examined 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. 

The 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.

"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 gives compelling evidence that breast density should not be the only criteria to guide decisions about supplemental screen, Dolan said.