Biopsy Study Illuminates Breast Cancer Risk

A new study should help women who have benign breast biopsies understand their cancer risk.

As mammography use increases, so does the frequency of breast biopsies, which usually are benign, or cancer-free, the authors write today in The New England Journal of Medicine. Each year, they say, more than 1 million U.S. women have benign breast biopsies. The new study focused on 9,087 women 18 to 85 who had a benign breast biopsy at the Mayo Clinic in Rochester, Minn., from 1967 through 1991. During 15 years’ follow-up on average, 707 were diagnosed with breast cancer.

A breast pathologist who did not know the original findings or the women’s current health classified stored slices of their biopsies into one of three categories: non-proliferative (no cell overgrowth), proliferative (overgrowth of normal cells) and atypical (overgrowth of abnormal cells). Scientists also asked the women about their family history of breast cancer.

About two-thirds of the biopsies contained non-proliferative changes, while 30% had an overgrowth of normal cells and 4% had an overgrowth of abnormal cells. Women with non-proliferative changes — such as a cyst — did not have an increased breast cancer risk as long as they did not have a strong family history.

If they did have a strong family history, they were about 60% more likely to be diagnosed with the disease than women in the general population. Strong family history was defined as having a first-degree relative — mother, sister or daughter — diagnosed before age 50 or at least two affected relatives, with at least one a first-degree relative.

Among women with an overgrowth of normal cells, those without a strong family history also were about 60% more likely to be diagnosed with breast cancer than women in the general population. If they had a strong family history, their breast cancer risk was about twice that of the general population.

Family history did not significantly affect breast cancer risk in women whose biopsies contained abnormal cells. Overall, they were about 300% more likely to be diagnosed with the disease than women in the general population.

An accompanying editorial points out the need to explain that these risk levels translate into relatively few cancer cases. In the study, about five out of 100 women in the general population developed breast cancer within 15 years, write editorial authors Joann Elmore of the University of Washington and Gerd Gigerenzer of Berlin’s Max Planck Institute. So doubling the risk raises the number of cases to 10 out of 100.

What should women at increased risk do? They could take tamoxifen, shown to reduce the risk of a breast cancer diagnosis, or enter a study of another drug or a screening tool, says Mayo cancer doctor Lynn Hartmann, lead study author. Vanderbilt University cancer pathologist David Page, who published similar findings in 1985, says his advice to higher-risk women — “because we don’t know to do anything better” — has been to get regular mammograms.