Abstract 3381: Standardizing the analysis of Ki-67 immunohistochemical assays
Authors: Liu Tian Yu , Chang Trillium , Adeoye Adewunmi , Shi Willa , Liang Sheng-Ben , Chadwick Dianne , Roehrl Michael H.A. , Miller Naomi , Liu Fei-Fei , Done Susan J. 
Published: August 2015

Intro

Immunohistochemical assays of the proliferation marker, Ki-67, have been associated with poorer clinical prognosis in breast cancer. However, a high degree of inconsistency in scores has been demonstrated in inter-laboratory and intra-laboratory Ki-67 positivity scorings, this has limited its potential in clinical practice. In this study, we aim to find a more consistent method for scoring Ki-67 positivity among malignant breast tumours.

Methods

Six Tissue Microarray (TMA) blocks were sectioned and immunohistochemistry was performed with Anti-Ki-67 antibody. Slides were then evaluated and Ki-67 positive cells in invasive breast carcinoma were scored as a percent positivity manually by a trained analyst with random sample quality assurance (QA) by trained pathologists. This was used as the standard benchmark for the experiment as it has been correlated successfully with clinical outcome. Successively, the same six slides were then annotated on Aperio ePathology software by two observers with different levels of pathology training and experience. The annotated regions were analyzed for Ki-67 positivity with Aperio ePathology software on UHN BioBank servers. The computer analyzed scores were compared to the manual benchmark scores.

Results

The difference between computer-analyzed and manual-scores were relatively large, Observer-A-annotated-computer-analyzed vs. analyst-manual-scores had a difference of 4.23% to 16.96%, while Observer-B-annotated-computer-analyzed vs. analyst-manual-scores had a difference of 7.13% to 15.03%. Interestingly, Observer-A-annotated-computer-analyzed vs. Observer-B-annotated-computer-analyzed scores only had a difference of 0.49% to 2.91%. Pearson Correlation was calculated for all samples on a case-by-case basis and we found there to be a linear correlation of 0.564, with a P-value of 3.6082×10-8, between the computer scores and the manual scores; suggesting significant correlation between the computer scores and the manual score.

Conclusion

A significant linear correlation has been observed between the computer score and the manual score. However, while the data does not seem to support the idea that a semi-automatic method of computer scoring will replace analyst manual scoring, most of the large contributing variables have been identified. We plan in the next steps of the project to continue to decrease the effects of such variables. It is interesting that the inter-observer computer score displayed a minimal amount of difference, again with the variables identified. This could signify a more consistent method of Ki-67 scoring. Further experiments will be conducted to continue to reduce the variables and optimize the system to gain similar performance as manual scoring. Hopefully in the near future, computerized immunohistochemical analysis can replace the tedious task of manual scoring.

Citation Format: Tian Yu Liu, Trillium Chang, Adewunmi Adeoye, Willa Shi, Sheng-Ben Liang, Dianne Chadwick, Michael H.A. Roehrl, Naomi Miller, Fei-Fei Liu, Susan J. Done. Standardizing the analysis of Ki-67 immunohistochemical assays. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3381. doi:10.1158/1538-7445.AM2015-3381