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

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.

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.

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).

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.