A woman whose mammogram shows evidence of "dense" breast tissue is not automatically at higher risk for breast cancer and may not need further imaging tests, doctors are suggesting.
While breast density has been linked to an increased cancer risk, and can make an existing cancer harder to detect by screening tumors from X-rays, not all women with dense breast tissue are at high risk, they say.
Researchers in a study led by the University of California San Francisco have gathered data on exactly what is the level of cancer risk for women with dense breast tissue.
They have concluded an elevated level of risk will involve only 24 percent of women with breasts that are either extremely dense tissue or which are dense throughout and then likely only if they have they have additional risk factors.
Those factors could include age, ethnicity, or family health history of cancer.
"Breast density should not be the sole criterion for deciding whether supplemental imaging is justified because not all women with dense breasts have high interval cancer rates," researcher Karla Kerlikowske at the San Francisco Veterans Affairs Medical Center and her colleagues report in the journal Annals of Internal Medicine.
Around 45 percent of women have breasts that are considered dense, but that does not automatically suggest a need for extra tests such as ultrasound exams or an MRI, the researchers say.
"We found that for the vast majority of women undergoing mammography - including those with dense breasts but low five-year breast cancer risk - the chance of developing breast cancer within 12 months of a normal mammogram was low," says Kerlikowske.
The debate over whether dense breast tissue on a mammogram should automatically suggest further testing has been going on for some time, and 22 U.S. states have put laws on the books under which doctors who receive mammogram results of dense breast tissue must discuss possible additional screening options with their patients.
A federal law with similar requirements is also being reviewed.
Kerlikowske says that may be overcautious.
"You can't do supplemental screening for 45 percent of the population," she says, referring to the portion of women who routinely show dense tissue in a mammogram. "It's just not realistic, neither from a time nor cost standpoint."
The takeaway finding of the study, write Nancy Dolan and Mita Sanghavi Goel from the Northwestern University Feinberg School of Medicine in an accompanying editorial, is that there "compelling evidence that breast density should not be the sole criterion to guide decisions about supplemental breast cancer screening."
