The ITT unadjusted analysis for the whole cohort, and among women with ER positive BC, showed that iDFS was slightly improved for patients assigned to 12 years tamoxifen compared to those assigned to 2–3 years (HR = 0.90 (95% CI: 0.81–0.99), p = 0.045 and HR = 0.90 (0.79–1.03), p = 0.118, respectively). This evidence concerns the gene ESR1 and breast cancer.