Real-World Association of HER2/ ERBB2 Concordance with Trastuzumab Clinical Benefit in Advanced Esophagogastric Cancer

Aim: To assess concordance between HER2 status measured by traditional methods and ERBB2 amplification measured by next-generation sequencing and its association with first-line trastuzumab clinical benefit in patients with advanced esophagogastric cancer. Methods: Retrospective analysis of HER2/ ERBB2 concordance using a deidentified USA-based clinicogenomic database. Clinical outcomes were assessed for patients with HER2 + advanced esophagogastric cancer who received first-line trastuzumab. Results: Overall HER2/ ERBB2 concordance was 87.5%. Among patients who received first-line trastuzumab, concordant HER2/ ERBB2 was associated with longer time to treatment discontinuation (adjusted hazard ratio [aHR]: 0.63; 95% CI: 0.43–0.90) and overall survival (aHR: 0.51; 95% CI: 0.33–0.79). ERBB2 copy number ≥25 (median) was associated with longer time to treatment discontinuation (aHR: 0.56; 95% CI: 0.35–0.88) and overall survival (aHR: 0.52; 95% CI: 0.30–0.91). Conclusion: HER2/ ERBB2 concordance and higher ERBB2 copy number predicted clinical benefit from trastuzumab.