Two years of tamoxifen prolonged RFi at 10 years and at full follow-up in patients with ER-positive (ER+) or PR-positive (PR+) tumours by each method (HR and 95% CI) at 10 years: cytosol-ER+ 0.56 (0.36–0.89), p = 0.014; IHC-ER+ 0.58 (0.38–0.88), p = 0.011; GEX-ER+ 0.58 (0.39–0.87), p = 0.009; cytosol-PR+ 0.54 (0.35–0.83), p = 0.005; IHC-PR+ 0.60 (0.38–0.93), p = 0.021; GEX-PR+ 0.60 (0.39–0.91), p = 0.016. The gene discussed is ESR1; the disease is neoplasm.