The PEPI analyzes the post-surgical specimen and combines tumor size (T1/2 vs. T3/4), nodal status (positive or negative), Ki67 level, and ER Allred Score (0–2 vs. 3–8), which were all associated with RFS, to give a score of 0, 1–3, or ≥ 4 (Additional file 1. This evidence concerns the gene ESR1 and neoplasm.