Racial and ethnic disparities in breast cancer: a multilevel perspective.

Although the etiology of racial and ethnic disparities in breast cancer is complex, the studies reviewed here suggest many possible culprits. In the authors' model, outcomes at the cellular level reflect not only genetic constitution and the hormonal milieu but also the interactions of predictors at multiple levels. At the societal level, important predictors include toxin and hormone exposure, access to care, quality of care, and social support. At the individual level, reproductive history, exogenous hormone use, diet,exercise, and response to stress all may influence cellular outcomes. The smooth transition from normal cell function to apoptosis occurs when the interactions between factors at the societal, individual, and cellular levels are harmonious. Perturbations at the societal level, however, such as inferior quality of care, or at the individual level, such as exogenous hormone use,can have profound effects on cell biology and predispose to neoplasia. When these perturbations are systematic and vary by race or ethnicity, disparities in breast cancer incidence and mortality result. Increasing incidence of breast cancer among both men and women likely reflects important trends at the societal and individual levels. These trends may include increased toxin exposure, increased obesity, and changes in the timing and number of births. Efforts to reduce breast cancer incidence and disparities must consider societal and individual factors and the important effects these factors can have on normal cell function.