Women with larger breasts have a greater risk of developing breast cancer before menopause than smaller-breasted women do, a new study shows.

While the findings are useful for breast cancer researchers, they have no real implications for women themselves, the study’s principal author, Karin B. Michels of the Harvard School of Public Health in Boston, told Reuters Health. “If you have small breasts, you’re not safe,” she stressed. “Screening should be for all women, not only for women with larger breasts.”

Studies investigating the association between breast size and breast cancer risk have had mixed results, Michels and her colleagues note. To provide a more definitive answer, they looked at 89,268 women between the ages of 29 and 47, all of whom reported their bra cup size at age 20. The study was prospective, meaning that participants were followed over time to see if they developed breast cancer.

Among lean women, Michels and her team found, women with bra sizes of D or larger had an 80-percent greater risk of developing breast cancer during the study’s follow-up period than those with a smaller cup size. However, there was no link between bra cup size and breast cancer risk among overweight or obese women.

This is because cup size is most accurate for measuring breast size in thinner women, Michels said. Increased risk with larger breasts most likely occurs for all women, she added, but bra size is a less accurate gauge of breast size among heavier women.

The findings are simple, she added: “The bigger the breast, the more breast cells. The more cells you have, the more cells are at risk for a potential mutation or malignant change.”

SOURCE: International Journal of Cancer, April 15, 2006.