Bouchard-Fortier et al. reported that breast cancer patients with weak ER expression (< 10 fmol/mg cytosol protein) do not significantly benefit from adjuvant antihormonal therapy (tamoxifen) compared with those exhibiting higher ER levels (≥ 10 fmol/mg cytosol protein) on a ligand-based assay (LBA) [34]. Here, ESR1 is linked to breast cancer.