ESR1 and breast cancer: While multigene assays such as Oncotype DX® have certainly allowed for a more individualized approach to the risk-stratification of estrogen receptor positive, HER2 negative breast cancer patients, multigene assays are costly (Oncotype DX® costs more than USD $4000.00), and may not be accessible to breast cancer patients without adequate health insurance, particularly in more poverty stricken geographies around the world.