ESMO Congress 2023 | OncologyPRO

Abstract 123P

Background

HER2 is overexpressed in a subset of BTC patients, and recent developments in HER2-targeted agents are expanding therapeutic options. However, accurately assessing HER2 expression is challenging in BTC, especially at a low-expression level. We evaluated HER2 expression as well as TILs density through AI models in BTC.

Methods

Whole-slide images (WSI) of pre-treatment HER2 immunohistochemistry (IHC) slides, matched H&E-stained slides and clinicopathological data were obtained from advanced or metastatic BTC patients at CHA Bundang Medical Center in South Korea, between 2019 and 2022. An AI-powered HER2 analyzer classifies tumor cells by HER2 staining intensity (H0, H1, H2, or H3) and quantifies the cells in each staining category. Then, it calculates HER2 categories (0/1+/2+/3+) following the latest ASCO/CAP HER2 IHC guidelines. For evaluating immune landscape, a separate WSI analyzer identified and quantified. TILs within the cancer epithelium or stroma from H&E-stained slides.

Results

In a total of 328 patients, the AI-scored HER2 categories were 0 in 92 (28.9%), 1+ in 137 (43.1%), 2+ in 68 (21.4%), and 3+ in 21 (6.6%). The overall concordance of HER2 categories between the AI and pathologists’ readings was 75.3%. HER2 3+ rates by AI in intrahepatic, extrahepatic, gallbladder, and Ampulla of Vater are estimated to be 3.1%, 3.4%, 21.4%, and 5.9%, respectively. HER2-expressing tumors (1+, 2+, and 3+) have significantly higher densities of stromal TILs (983.2 ± 1347.5 / mm2) than HER2-negative tumors (683.5 ± 739.7 / mm2, p=0.012) and there were no significant TIL density differences between HER2-high expressing (3+) and low expressing tumors (1+, 2+), which were consistent with either by the AI or pathologists.

Conclusions

AI-powered HER2 scoring showed good agreement with pathologists’ scoring, and HER2-expressing tumors harbored high stromal TIL in BTC. Objective expression analysis and the associated differences in immunogenicity will be important for future treatment strategies.