Targeted drugs and diagnostic assays: Companions in the race to combat ethnic disparity.

African Americans (AAs) are more likely than European Americans to develop aggressive breast cancer subtypes, and have higher recurrence and mortality rates; this results in a stark breast-cancer related ethnic disparity in clinical outcomes. In this era of personalized oncology, companion diagnostics (CDx) are transforming the cancer treatment narrative slowly but steadily, by enabling the use of safety and/or efficacy biomarkers to stratify patient populations, and thus ensuring more effective deployment of targeted therapeutics. This parallel co-development of drugs and in vitro diagnostic assays is turning out to be the cornerstone of individualized cancer treatment. In this review, we assert that development of drugs and CDx targeted towards molecular and centrosomal aberrations that occur more frequently in AAs could yield next generation precision medicine tools better informed and inspired by, and more finely attuned to the unique tumor biology of AAs. By understanding more deeply ancestry-associated differences among breast tumors of different ethnicities, and gearing our drug and CDx development efforts to target these distinctions, we might be able to significantly alleviate racial health disparity.