Aims In the DESTINY-Gastric01 trial, a novel HER2-targeted antibody-drug conjugate trastuzumab deruxtecan proved to be effective in HER2-low gastro-oesophageal adenocarcinomas. The aim of our study is to investigate the clinicopathological and molecular features of HER2-low gastric/gastro-oesophageal junction cancers in the real-world setting of a large multi-Institutional series.
Methods We retrospectively evaluated 1210 formalin-fixed paraffin-embedded samples of gastro-oesophageal adenocarcinomas which were analysed by immunohistochemistry for HER2 protein expression in 8 Italian surgical pathology units from January 2018 to June 2022. We assessed the prevalence of HER2-low (ie, HER2 1+ and HER2 2+ without amplification) and its correlation with clinical and histopathological features, other biomarkers’ status, including mismatch repair/microsatellite instability status, Epstein-Barr encoding region (EBER) and PD-L1 Combined Positive Score.
Results HER2 status could be assessed in 1189/1210 cases, including 710 HER2 0 cases, 217 HER2 1+, 120 not amplified HER2 2+, 41 amplified HER2 2+ and 101 HER2 3+. The estimated prevalence of HER2-low was 28.3% (95% CI 25.8% to 31.0%) overall, and was higher in biopsy specimens (34.9%, 95% CI 31.2% to 38.8%) compared with surgical resection specimens (21.0%, 95% CI 17.7% to 24.6%) (p<0.0001). Moreover, HER2-low prevalence ranged from 19.1% to 40.6% among centres (p=0.0005).
Conclusions This work shows how the expansion of the HER2 spectrum might raise problems in reproducibility, especially in biopsy specimens, decreasing interlaboratory and interobserver concordance. If controlled trials confirm the promising activity of novel anti-HER2 agents in HER2-low gastro-oesophageal cancers, a shift in the interpretation of HER2 status may need to be pursued.
- Gastrointestinal Neoplasms
- Biomarkers, Tumor
Data availability statement
Data are available on reasonable request to the corresponding authors.
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Handling editor Deepa Patil.
LM and MF contributed equally.
Contributors VA, PP, AV, FG, LM and MF conceptualised and designed the study. VA, PP, MC, CU, SB, PC, AG and GDL collected samples and provided clinical data. VA, PP, MC, CU, SB, PC, AG, GDL, AV, FG, LM and MF provided histopathology expertise. VA, PP and FC performed the data analysis. VA, PP, AV, FG, LM and MF contributed to interpretation of the results. VA, PP, AV, FG, LM and MF wrote the first draft of the manuscript, and all authors critically revised the manuscript. LM and MF guarantors of the manuscript. All authors approved the final version of the manuscript.
Funding MF is supported by grants from the Italian Health Ministry/Veneto region research programme NET-2016-02363853 and AIRC 5 per mille 2019 (ID. 22759 programme). LM is supported by grants from the Italian Ministry of Health (5×1000—2018/2019).
Disclaimer The funding agencies had no role in the design and performance of the study.
Competing interests MF has been involved in consulting/advisory roles in Astellas Pharma, Pierre Fabre, MSD, GlaxoSmithKline, Amgen, Novartis and Roche, and received research funding from Astellas Pharma, QED Therapeutics, Diaceutics and Macrophage Pharma.
Provenance and peer review Not commissioned; externally peer reviewed.