Tamoxifen improved RFi in patients with ER-positive (ER+) or PR-positive (PR+) tumours (Hazard Ratio [HR] and 95% confidence interval [CI]), cytosol-ER+ 0.53 [0.36–0.79]; IHC-ER+ 0.55 [0.38–0.79]; GEX-ER+ 0.54 [0.37–0.77]; cytosol-PR+ 0.49 [0.34–0.72]; IHC-PR+ 0.58 [0.40–0.85]; GEX-PR+ 0.55 [0.38–0.80]). Here, ESR1 is linked to neoplasm.