The role of artificial intelligence in accurate interpretation of HER2 IHC 0 and 1+ in breast cancers

Abstract The new HER2-targeting antibody drug conjugate offers the opportunity to treat patients with HER2-low breast cancer. Distinguishing HER2 immunohistochemistry (IHC) scores of 0 and 1+, is critical but also challenging due to HER2 heterogeneity and variability of observers. In this study, we aimed to increase interpretation accuracy and consistency of HER2 IHC 0 and 1 + evaluations through assistance from artificial intelligence (AI) algorithm. In addition, we examined the value of AI algorithm in evaluating HER2 IHC scores in tumors with heterogeneity. The AI-assisted interpretation consisted of AI algorithms and an augmenting reality module with microscope. Fifteen pathologists (5 junior, 5 mid-level and 5 senior) participated this multi-institutional two-round ring study that included 246 infiltrating duct carcinoma not otherwise specified (NOS) cases. In round 1, pathologists analyzed 246 HER2 IHC slides by microscope without AI assistance. After 2 weeks of washout period, the pathologists read the same slides with AI algorithm assistance and rendered the final results by adjusting to the AI algorithm. The interpretation accuracy was significantly increased with AI assistance (Accuracy 0.93 vs 0.80), as well as the evaluation precision of HER2 0 and the recall of HER2 1+. The AI algorithm also improved the total consistency (ICC = 0.542 to 0.812), especially in HER2 1 + cases. In cases with heterogeneity, the accuracy was improved significantly (Accuracy 0.68 to 0.89) and to similar level as cases without heterogeneity (Accuracy 0.95). Both accuracy and the consistency of junior pathologists were better improved than the mid-level and senior pathologists. To the best of our knowledge, it is the first study to show that the accuracy and consistency of HER2 IHC 0 and 1 + evaluations and the accuracy of HER2 IHC evaluation in breast cancers with heterogeneity can be significantly improved using AI-assisted interpretation.