Analytical validation of a standardised scoring protocol for Ki67 immunohistochemistry on breast cancer excision whole sections: an international multicentre collaboration

Abstract

Aims The nuclear proliferation marker Ki67 assayed by immunohistochemistry has multiple potential uses in breast cancer, but an unacceptable level of interlaboratory variability has hampered its clinical utility. The International Ki67 in Breast Cancer Working Group has undertaken a systematic programme to determine whether Ki67 measurement can be analytically validated and standardised among laboratories. This study addresses whether acceptable scoring reproducibility can be achieved on excision whole sections. Methods and results Adjacent sections from 30 primary ER+ breast cancers were centrally stained for Ki67 and sections were circulated among 23 pathologists in 12 countries. All pathologists scored Ki67 by two methods: (i) global: four fields of 100 tumour cells each were selected to reflect observed heterogeneity in nuclear staining; (ii) hot‐spot: the field with highest apparent Ki67 index was selected and up to 500 cells scored. The intraclass correlation coefficient (ICC) for the global method [confidence interval (CI) = 0.87; 95% CI = 0.799–0.93] marginally met the prespecified success criterion (lower 95% CI ≥ 0.8), while the ICC for the hot‐spot method (0.83; 95% CI = 0.74–0.90) did not. Visually, interobserver concordance in location of selected hot‐spots varies between cases. The median times for scoring were 9 and 6 min for global and hot‐spot methods, respectively. Conclusions The global scoring method demonstrates adequate reproducibility to warrant next steps towards evaluation for technical and clinical validity in appropriate cohorts of cases. The time taken for scoring by either method is practical using counting software we are making publicly available. Establishment of external quality assessment schemes is likely to improve the reproducibility between laboratories further.

Prognostic potential of automated Ki67 evaluation in breast cancer: different hot spot definitions versus true global score

“…The larger the number of investigated cells, the higher the reproducibility between the apps in the group. The median Ki67 value was higher across all DIA hot spot apps (21-35%) and manual hot spot scoring (20%) as compared to the global DIA Ki67 scoring (15.9%), which is in line with previous published data [38].…”

“…There is increasing evidence suggesting that global or average scoring of Ki67 is favorable over hot spot scoring methods, and here Leung et al suggest against the use of manual Ki67 hot spot scoring due to poor reproducibility [37,38]. The IKWG also point to the methodological aspects for improvement of Ki67 assessment [24,38]. In a study by Jang et al manual average and hot spot methods for Ki67 scoring among HR+/HER2− tumors was compared and both methods showed good predictive performances for recurrence; however, the average method showed higher reproducibility [39].…”

“…Pre-analytical and analytical aspects along with poor interlaboratory scoring reproducibility are some of the identified causes of variability in Ki67 assessment, which has limited the international adoption in clinical breast cancer management [18,19,21]. There is increasing evidence suggesting that global or average scoring of Ki67 is favorable over hot spot scoring methods, and here Leung et al suggest against the use of manual Ki67 hot spot scoring due to poor reproducibility [37,38]. The IKWG also point to the methodological aspects for improvement of Ki67 assessment [24,38].…”

Luminal A versus luminal B breast cancer: MammaTyper mRNA versus immunohistochemical subtyping with an emphasis on standardised Ki67 labelling‐based or mitotic activity index‐based proliferation assessment

“…When a field contained < 170 cells, it was expanded by counting additional tumour cells in a neighbouring field. The Ki67‐G and Ki67‐H methods are similar but not identical to the recently published weighted and unweighted Ki67 scores of the International Ki67 in Breast Cancer Working Group, as the estimated percentage of the total cancer area covered by each of high, medium, low or negligible Ki67 staining 22,23 was not taken into account for our assessment.…”

<p>Gallic Acid Impedes Non-Small Cell Lung Cancer Progression via Suppression of EGFR-Dependent CARM1-PELP1 Complex</p>

“…Ki67 has been known to be a proliferation marker in the prognosis of cancers. 21,22 Fas and FasL are two receptors capable of stimulating cell apoptosis. 23,24 Fas and FasL have been illustrated previously to be increased by gallic acid, thereby inducing apoptosis of lung fibroblasts.…”