Trainable immunohistochemical HER2/neu image analysis: a multisite performance study using 260 breast tissue specimens.

Context: Aperio Technologies, Inc (Vista, California) provides a new immunohistochemistry (IHC) HER2 Image Analysis (IA) system that allows tuning of the intensity thresholds of the HER2/ neu scoring scheme to adapt to the staining characteristics of different reagents.

Objective: To compare the trainable IHC HER2 IA system for different reagents to conventional manual microscopy (MM) in a multisite study.

Design: Two hundred sixty formalin-fixed, paraffin-embedded breast cancer specimens from 3 clinical sites were assayed: 180 specimens stained with Dako's HercepTest (Carpinteria, California), and 80 specimens stained with Ventana's PATHWAY HER-2/neu (Tucson, California). At each site, 3 pathologists performed a blinded reading of the glass slides with the use of a light microscope. The glass slides were then scanned and after a wash-out period and randomization, the same pathologists outlined a representative set of tumor regions to be analyzed by IHC HER2 IA. Each of the methods, MM and IA, was evaluated separately and comparatively by using κ statistics of negative HER2/neu scores (0, 1+) versus equivocal HER2/neu scores (2+) versus positive HER2/neu scores (3+) among the different pathologists.

Results: κ Values for IA and MM were obtained across all sites. MM: 0.565-0.864; IA: 0.895-0.947; MM versus IA: 0.683-0.892 for site 1; MM: 0.771-0.837; IA: 0.726-0.917; MM versus IA: 0.687-0.877 for site 2; MM: 0.463-0.674; IA: 0.864-0.918; MM versus IA: 0.497-0.626 for site 3.

Conclusion: Aperio's trainable IHC HER2 IA system shows substantial equivalence to MM for Dako's HercepTest and Ventana's PATHWAY HER-2/neu at 3 clinical sites. Image analysis improved interpathologist agreement in the different clinical sites.