Challenges in studying the etiology of breast cancer subtypes.

Research that classifies breast tumors into homogenous subgroups could ultimately help to define public health prevention strategies for aggressive breast cancer subtypes. However, etiologic research on molecular breast cancer subtypes must overcome several challenges. Stratifying breast cancers into subgroups can reduce statistical power and, therefore, may require non-traditional analytical methods. Integrating results across studies is hampered by varying definitions of molecular subtypes, with some studies using triple negative status and others using specific markers to define basal-like cancers. In addition, triple negative and basal-like breast cancers appear to show strong associations with race, so the varied racial and ethnic composition of different datasets can make comparison across studies challenging. In spite of these challenges, some strong and consistent associations between triple negative or basal-like breast cancer and demographic variables are emerging, and there are hints that prevention strategies for this aggressive subtype of breast cancer may also be attainable.