Researchers from the Mayo Clinic have reported that benign breast disease increases the risk of developing breast cancer. The details of this retrospective study appeared in the July 21, 2005, issue of the New England Journal of Medicine. [1]

Benign breast disease is relatively common in women and has been associated with an increased chance of developing breast cancer. These authors point out that 20% of women will undergo a breast biopsy sometime in their life, and the majority of these biopsies are benign. Such benign lesions are classified as non-proliferative, proliferative lesions without atypia or proliferative lesions with atypia (atypical hyperplasia). In this study, researchers looked at 9,087 women who had breast biopsies that showed benign breast disease and had been followed for an average of 15 years.

During this period of time, 707 breast cancers were diagnosed in this cohort of women. Compared with women in the general population, women with nonproliferative findings had a 27% increased risk of breast cancer, those with proliferative changes without atypia had an 88% increased risk and those with atypical hyperplasia had a four-fold increase in risk of breast cancer.

In the accompanying editorial it was pointed out that it was important to translate these risks in a meaningful way to patients.[2] As an example, the editorial pointed out that a 27% increase in breast cancer means that 6 out of 100 women with nonproliferative changes will develop breast cancer rather than the expected number of 5 in women in the general population.

They also pointed out that an 88% increase in breast cancer in women with proliferative lesions would increase the incidence from a background of 5 to approximately 10 per 100 women. They also calculated that for women with atypical hyperplasia the four-fold increase translates to an increase in breast cancer from 5 in the normal population to 19.

The other risk factor that contributed independently to an increased incidence of breast cancer was family history. They observed that women with nonproliferative findings and a negative family history for breast cancer were not at an increased risk for breast cancer.

These findings may help in assessing women who are at increased risk of breast cancer. The accompanying editorial should be very helpful in informing physicians of the best way to express increased breast cancer risk to patients.

References:

[1] Hartmann LC, Sellers TA, Frost MH, et al. Benign breast disease and the risk of breast cancer. New England Journal of Medicine. 2005;353:229-237.

[2] Elmore JG and Gigerenzer G. Benign breast disease-risks of communicating risk. New England Journal of Medicine. 2005;353:297-299.

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