Analytical validation of a standardised scoring protocol for Ki67 immunohistochemistry on breast cancer excision whole sections: an international multicentre collaboration PMID: 31017314

ADC Targets in Oncology

2026-04-10

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

Histopathology. 2019 Aug;75(2):225-235. doi: 10.1111/his.13880.

Samuel C Y Leung ¹ , Torsten O Nielsen ¹ , Lila A Zabaglo ² , Indu Arun ³ , Sunil S Badve ⁴ , Anita L Bane ⁵ , John M S Bartlett ⁶ ⁷ , Signe Borgquist ⁸ , Martin C Chang ⁹ , Andrew Dodson ¹⁰ , Anna Ehinger ¹¹ , Susan Fineberg ¹² , Cornelia M Focke ¹³ , Dongxia Gao ¹ , Allen M Gown ¹⁴ , Carolina Gutierrez ¹⁵ , Judith C Hugh ¹⁶ , Zuzana Kos ¹⁷ , Anne-Vibeke Laenkholm ¹⁸ , Mauro G Mastropasqua ¹⁹ , Takuya Moriya ²⁰ , Sharon Nofech-Mozes ²¹ , C Kent Osborne ¹⁵ , Frédérique M Penault-Llorca ²² , Tammy Piper ⁷ , Takashi Sakatani ²³ , Roberto Salgado ²⁴ ²⁵ , Jane Starczynski ²⁶ , Tomoharu Sugie ²⁷ , Bert van der Vegt ²⁸ , Giuseppe Viale ¹⁹ ²⁹ , Daniel F Hayes ³⁰ , Lisa M McShane ³¹ , Mitch Dowsett ² , International Ki67 in Breast Cancer Working Group of the Breast International Group and North American Breast Cancer Group (BIG-NABCG)

Affiliations

1. University of British Columbia, Vancouver, BC, Canada.
2. The Institute of Cancer Research, London, UK.
3. Tata Medical Center, Kolkata, India.
4. Indiana University Simon Cancer Center, Indianapolis, IN, USA.
5. Juravinski Hospital and Cancer Centre, McMaster University, Hamilton, ON, Canada.
6. Ontario Institute for Cancer Research, Toronto, ON, Canada.
7. Edinburgh Cancer Research Centre, Western General Hospital, Edinburgh, UK.
8. Division of Oncology and Pathology, Department of Clinical Science, Lund University, Lund, Sweden.
9. Department of Pathology and Laboratory Medicine, University of Vermont Medical Center, Burlington, VT, USA.
10. Ralph Lauren Centre for Breast Cancer Research, The Royal Marsden Hospital, London, UK.
11. Department of Clinical Genetics and Pathology, Skane University Hospital, Lund University, Lund, Sweden.
12. Montefiore Medical Center and the Albert Einstein College of Medicine, Bronx, NY, USA.
13. Dietrich-Bonhoeffer Medical Center, Neubrandenburg, Germany.
14. PhenoPath Laboratories, Seattle, WA, USA.
15. Lester and Sue Smith Breast Center and Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA.
16. University of Alberta, Edmonton, AB.
17. University of Ottawa and The Ottawa Hospital, Ottawa, ON, Canada.
18. Department of Surgical Pathology, Zealand University Hospital, Slagelse, Denmark.
19. European Institute of Oncology, Milan, Italy.
20. Kawasaki Medical School, Kurashiki, Japan.
21. University of Toronto Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
22. Centre Jean Perrin and Université d'Auvergne, Clermont-Ferrand, France.
23. Nippon Medical School, Bunkyo-ku, Japan.
24. Department of Pathology, GZA-ZNA, Antwerp, Belgium.
25. Division of Research, Peter MacCallum Cancer Centre, Melbourne, Australia.
26. Birmingham Heart of England, National Health Service, Birmingham, UK.
27. Kansai Medical University, Hirakata, Japan.
28. University Medical Center Groningen, Groningen, the Netherlands.
29. University of Milan, Milan, Italy.
30. University of Michigan Rogel Cancer Center, Ann Arbor, MI, USA.
31. National Cancer Institute, Bethesda, MD, USA.

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.

Keywords

Ki67; analytical validity; immunohistochemistry; interobserver reproducibility; interobserver variability; pathology; scoring protocol.