Certain features on normal mammograms of women under age 50 may help doctors predict future breast cancers.
Researchers in the Public Health Sciences Division recently found that younger women whose mammograms reveal large regions of breast density or certain types of mineral deposits (calcifications) have a high risk of developing breast cancer.
The finding may let radiologists decide whether a woman is a good candidate for more intensive cancer screening, said Dr. David Thomas, lead author of the study.
Results were published in the June issue of Cancer Epidemiology, Biomarkers & Prevention and involved collaborators in the Clinical Research Division and at the University of Washington.
Radiologists in the study evaluated mammograms of 547 women under age 50 who later developed breast cancer and 472 women under 50 who did not develop the disease. In their review of mammograms, the radiologists did not know the subsequent breast cancer status of the women.
Four times more likely
Researchers found that a woman's risk of developing future breast cancer increased with the percentage of the area of dense tissue. Women with more than 70 percent dense breast tissue were four times more likely to develop cancer than women with low levels of breast density.
Some types of calcifications also were found to predict subsequent breast cancer, causing a two- to three-fold risk compared to women lacking calcifications.
Most significant was the increased risk—up to 10-times higher—calculated for women with both a high percentage of dense breast tissue and certain types of calcifications. Although previous studies have examined the risk of density and calcifications independently, the PHS analysis is the first to look at their combined effects.
Dr. Constance Lehman, director of breast imaging at the Seattle Cancer Care Alliance, a UW associate professor of radiology and co-author of the study, said the findings can be put to practical use.
"Women who have these mammographic features need to be particularly vigilant about being screened for breast cancer," she said.
More common in young women
Breast density is much more common in young women than in older women, whose breasts tend to consist of more fatty tissue.
In part, because density tends to make mammograms more difficult to interpret and may mask radiological detection of breast tumors, the usefulness of mammograms for younger women is controversial, Thomas said.
"Still, many women under 50 do get mammograms," he said. "If that's the case, can radiologists get more useful information from them? Our results indicate that they can."
Although breast density can mask tumors, it is unlikely that all subsequent cancers observed in this study represent previously undetected cancers. Many women in the study were not diagnosed with cancer until six or more years after their mammograms revealed density and calcifications, a time frame longer than would be expected if their tumors had been present at that time.
Lehman said the study results represent yet another way to provide women with useful information about their cancer risk.
"We're learning more and more about risk factors for breast cancer," she said.
"It's been well known that density tends to hide cancers on the mammogram. It has also been shown that increased density can put a woman at increased risk for developing cancer.
"In this paper, we show certain types of calcifications, combined with increased breast density, are additional risk factors. It's more information we can share with women and their doctors to help them make decisions about their cancer risk."