Correlation between Ki67 and Histological Grade in Breast Cancer Patients Treated with Preoperative Chemotherapy

Background and Aim: Breast cancer (BC) is a heterogeneous disease and cell proliferation markers may helpto identify subtypes of clinical interest. We here analyzed the correlation between cell proliferation determinedby Ki67 and HG in BC patients undergoing preoperative chemotherapy (PCT). Materials and
Methods: Weobtained clinical/pathological data from patients with invasive BC treated at our institution from 1999 until2012. Expression of estrogen receptor (ER), progesterone receptor (PR), epidermal growth factor receptor type2 (HER2) and Ki67 were determined by immuno-histochemistry (IHC). Clinicopathological subtypes weredefined as: Luminal A, ER and/or PR positive, HER2 negative, HG 1 or 2; Luminal B, ER and/or PR positive,HER2 negative or positive and/or HG 3; triple negative (TN), ER, PR and HER2 negative independent ofHG; HER2 positive, ER, PR negative and HER2 positive, independent of HG. By using Ki67, a value of 14%separated Luminal A and B tumors, independently of the histological grade. We analyzed correlations betweenKi67 and HG, to define BC subtypes and their predictive value for response to PCT.
Results: 1,560 BC patientswere treated in the period, 147 receiving PCT (9.5%). Some 57 had sufficient clinicopathological information tobe included in the study. Median age was 52 years (26-72), with 87.7% invasive ductal carcinomas (n=50). Weperformed IHC for Ki67 in 40 core biopsies and 50 surgical biopsies, 37 paired samples with Ki67 before andafter chemotherapy being available. There was no significant correlation between Ki67 and HG (p=0.237), bothcategorizing patients into different subtypes. In most cases Ki67 decreased after PCT (65.8%). Only 3 patientshad pathologic complete response (cPR).
Conclusions: In our experience we did not find associations betweenKi67 and HG. Determination of clinicopathological luminal subtypes differs by using Ki67 or HG.