Breast Density Linked to Greater Cancer Risk

High density also decreases detection by mammography

WEDNESDAY, Jan. 17 (HealthDay News) -- Women who have dense breast tissue are less likely to have cancer detected during mammography and have an increased risk of breast cancer compared to women with tissue that is less dense, according to a report in the Jan. 18 issue of the New England Journal of Medicine.

Norman F. Boyd, M.D., from the Ontario Cancer Institute in Toronto, Canada, and colleagues examined the association between mammographic breast density and risk of breast cancer in 1,112 matched case-control pairs based on age, method of cancer detection and time since initiating screening.

The researchers found that a higher breast density was associated with a greater risk of breast cancer (odds ratio, 4.7 for density of 75 percent or greater versus density less than 10 percent). For women with a 75 percent or greater mammographic density, the odds ratio was 3.5 for breast cancer that was detected by screening and 17.8 for cancer detected within a year after a negative screening test. The increased risk was higher in younger women and continued for at least eight years after entering the study.

A substantial percentage of breast cancers can be attributed to high mammographic density, the report indicates.

"The time has come to acknowledge breast density as a major risk factor for breast cancer and to determine, develop and test the best ways to measure breast density in clinical practice, and use this measurement to maximize primary and secondary prevention of breast cancer," Karla Kerlikowske, M.D., of the University of California San Francisco, writes in an accompanying editorial.

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