The randomized phase III FALCON trial demonstrated superior efficacy in disease-free survival (DFS) in favor of 500 mg of fulvestrant compared to anastrozole in the first-line treatment of ER + metastatic breast cancer [23], consistent with the earlier FIRST randomized phase II study that suggested the superiority of fulvestrant over anastrozole in time to tumor progression [24]. This evidence concerns the gene ESR1 and neoplasm.