Although the most significant genes, such as BRCA1/2, can only predict or explain a portion of disease susceptibility, the number of genes examined in a single test has continually increased to improve accuracy.14, 50 Of particular note (Table 1), the 70-gene signature test for breast cancer (MammaPrint by Agendia)29 showed the most efficacy in a clinical trial.51 The study in 6693 women with early-stage breast cancer was conducted to examine whether the gene signature test could reduce the use of chemotherapy. Here, BRCA1 is linked to breast cancer.