Developing dual staining of HER2 IHC and ISH on AGCs on a single slide, along with a robust algorithm to determining HER2 status using deep learning

JSCO 2025 -- Stomach cancer is the fifth most common neoplasm and the third most deadly cancer, with a mere 5% to 10% five-year survival rate. Approximately 15%-20% of patients with advanced gastric and gastroesophageal junctional cancers (AGCs) exhibit overexpression or amplification of HER2. Trastuzumab in combination with chemotherapy has been the standard first-line treatment for HER2-positive GC following the TOGA trial. Phase 3 DESTINY-Gastric04: Trastuzumab deruxtecan can help HER2 positive patients with advanced gastric cancers live about 3 months longer. HER2 status (Pos/Neg) is currently determined using IHC and reflex FISH or ISH assay for IHC equivocal cases.