Improving Prognosis of Surrogate Assay for Breast Cancer Patients by Absolute Quantitation of Ki67 Protein Levels Using Quantitative Dot Blot (QDB) Method

Junmei Hao,Kuisheng Chen,Fangrong Tang,Wenfeng Zhang,Xunting Wang,Shuishan Xie,Jianbo Zhang,Jiahong Lyu,Jiandi Zhang,Yan Lyu,Jiarui Zou,Yunyun Zhang,Lili Jing

doi:10.3389/fonc.2021.737781

Abstract

BackgroundImmunohistochemistry (IHC)-based surrogate assay is the prevailing method in daily clinical practice to determine the necessity of chemotherapy for Luminal-like breast cancer patients worldwide. It relies on Ki67 scores to separate Luminal A-like from Luminal B-like breast cancer subtypes. Yet, IHC-based Ki67 assessment is known to be plagued with subjectivity and inconsistency to undermine the performance of the surrogate assay. A novel method needs to be explored to improve the clinical utility of Ki67 in daily clinical practice.Materials and MethodsThe Ki67 protein levels in a cohort of 253 specimens were assessed with IHC and quantitative dot blot (QDB) methods, respectively, and used to assign these specimens into Luminal A-like and Luminal B-like subtypes accordingly. Their performances were compared with the Kaplan–Meier, univariate, and multivariate survival analyses of the overall survival (OS) of Luminal-like patients.ResultsThe surrogate assay based on absolutely quantitated Ki67 levels (cutoff at 2.31 nmol/g) subtyped the Luminal-like patients more effectively than that based on Ki67 scores (cutoff at 14%) (Log rank test, p = 0.00052 vs. p = 0.031). It is also correlated better with OS in multivariate survival analysis [hazard ratio (HR) at 6.89 (95% CI: 2.66–17.84, p = 0.0001) vs. 2.14 (95% CI: 0.89–5.11, p = 0.087)].ConclusionsOur study showed that the performance of the surrogate assay may be improved significantly by measuring Ki67 levels absolutely, quantitatively, and objectively using the QDB method.

Highlights

Microarray analysis of global gene profiling (GEP) of breast cancer tissues leads to the identification of the four intrinsic subtypes: luminal, human epidermal growth factor receptor 2 (Her2)-like, basal-like, and normal-like subtypes [1, 2]
The surrogate assay based on absolutely quantitated Ki67 levels subtyped the Luminal-like patients more effectively than that based on Ki67 scores (Log rank test, p = 0.00052 vs. p = 0.031)
Our study showed that the performance of the surrogate assay may be improved significantly by measuring Ki67 levels absolutely, quantitatively, and objectively using the quantitative dot blot (QDB) method

Summary

Introduction

Microarray analysis of global gene profiling (GEP) of breast cancer tissues leads to the identification of the four intrinsic subtypes: luminal, Her2-like, basal-like, and normal-like subtypes [1, 2]. The Luminal-like patients are further separated into Luminal A (LumA) and Luminal B (LumB) patients. It is well accepted that LumA patients benefit less from chemotherapy than LumB patients [5]. Chemotherapy may be spared from many LumA patients, considering its strong side effects This concept has been well accepted with several GEP-based genetic tests developed to identify Luminal subtype patients who may be spared of chemotherapy [5]. Immunohistochemistry (IHC)-based surrogate assay is the prevailing method in daily clinical practice to determine the necessity of chemotherapy for Luminal-like breast cancer patients worldwide. It relies on Ki67 scores to separate Luminal A-like from Luminal B-like breast cancer subtypes. A novel method needs to be explored to improve the clinical utility of Ki67 in daily clinical practice

Methods

Results

Discussion

Conclusion