Risk factors for breast cancer from benign breast disease in a diverse population.

Background: The majority of studies have reported risks of breast cancer (BC) from benign breast disease (BBD) in essentially homogenous Caucasian populations. Information on breast cancer risk factors in larger, multi-ethnic populations should facilitate the development of appropriate and targeted risk reduction strategies.

Design: Cases and controls were drawn from a parent BBD cohort of 4,970 women, 1,341 African-Americans (AA) and 3,629 non-AA who were diagnosed with BBD after examination of an excisional breast biopsy. Risk factors (34 variables) included demographics, lesion types, and epidemiological variables.

Results: The final multivariable model retained significance (P < 0.05) for lesion risk-level, fibroadenoma, and the interaction of age-by-race. Women with proliferative lesions (no atypia, risk level 2) were 1.7 times more likely to develop BC when compared with women with non-proliferative lesions (OR = 1.7, 95% CI 1.13, 2.42, P = 0.009). Women with atypia (risk level 3) were 3.75 times more likely to develop BC compared to women with non-proliferative lesions (OR = 3.75, 95% CI 1.99, 7.06, P < 0.001). The odds of breast cancer was approximately 35% lower among women with fibroadenoma as compared to women without fibroadenoma (OR = 0.65, 95% CI 0.46, 0.94, P = 0.020). AA women with BBD who were 50 years or older were 2.28 times more likely to develop breast cancer as compared to non-AA women who were less than 50 years old (OR = 2.28, 95% CI 1.34, 3.88, P = 0.002).

Conclusion: Women with fibroadenoma (nonproliferative or proliferative) were less likely to progress to BC. Older AA women are at greater risk for progression to breast cancer from BBD.