Ki 67 Cut-off Level & mPEPI Score: Any Predictive Role for Neoadjuvant ‘Chemotherapy’ Efficacy in Locally Advanced HER2 Negative Luminal-like Breast Cancer?

Abstract Purpose:Role of neoadjuvant chemotherapy(NAC) & modified preoperative endocrine prognostic index (mPEPI) score after NAC is unclear in locally advanced HER2(-) breast cancer(LA-HnLBC).We evaluated prognostic & predictive factors for NAC in LA-HnLBC retrospectively. Methods:All had doxorubicin+/-taxane as NAC.They were grouped as pCR/non-pCR & categorized for PR/ki67/ki67 decline/mPEPI score. Ki67 cut-offs were as 20 & median values in our study. Results:142 LA-HnLBC pCR( n:26) & non-pCR(n:116) patients were included.Median age was 53 years. pCR rate was 18.3%. Median ER/PR/ki67 were as 90/40/40 %. Median ki67 was 40 for basal & postoperative. pCR group had more T2(73%), grade 3(69%) & non-pCR had more T3(21%), grade 2(46%) tumors (p=0.03,p=0.03). pCR group had lower mPEPI score (3.5 vs 5,p=0.05). 5y-DFS was 69% (93.8% vs 63.4%, p=0.012). 5y-OS was 77% (100% vs 72%, p=0.018). In univariate analysis, high basal/postoperative ki67 levels, ki67 decline & mPEPI score were significant poor prognostic factors for DFS (p=0.01, p< 0.001, p=0.017, p<0.001) & OS (p=0.006, p=0.003, p=0.05, p=0.001) in non-pCR goup. Prognostic cut-offs were as 40 for basal ki67 (DFS & OS), 20 for postoperative ki67 (DFS), 4 for mPEPI (DFS) & 30 for ki67 decline (OS). Conclusion: Favorable prognostic factors were defined as lower basal ki67 level (<40%) & higher ki67 decline (ki67 <30%) for OS; lower basal ki67 (<40%), po ki 67 (<20%) & mPEPI score (<4) for DFS after NAC in LA HnLBC. Different prognostic cut-offs for basal & postoperative ki 67 is striking. mPEPI score may also have prognostic significance after NAC, T in LA-HnLBC pts.