Companion Diagnostics Expand HER2 Testing in Metastatic Gastroesophageal Cancer

Gastric and esophageal cancers rank among the leading causes of cancer mortality worldwide, underscoring the importance of accurate biomarker testing to guide treatment decisions. A newly approved pair of companion diagnostics now expands HER2 testing for metastatic gastric, gastroesophageal junction, and esophageal adenocarcinoma.

Roche has announced that the U.S. Food and Drug Administration (FDA) has approved the expanded use of the PATHWAY HER2 (4B5) assay and VENTANA HER2 Dual ISH DNA Probe Cocktail to assess HER2-positive status in metastatic gastroesophageal adenocarcinoma (GEA). The authorization enables clinicians to identify HER2‑positive GEA patients who may be eligible for HER2‑targeted treatment with ZIIHERA (zanidatamab‑hrii), for which two regimens are approved in the first‑line setting for adults with unresectable locally advanced or metastatic HER2‑positive GEA. The approval newly extends HER2 testing to esophageal adenocarcinoma within this disease group.

The two assays are designed to be used together to determine HER2 status and support timely therapeutic decisions. The PATHWAY HER2 (4B5) immunohistochemistry (IHC) test demonstrates high concordance with fluorescence in situ hybridization (FISH) and is integrated into the fully automated VENTANA BenchMark slide‑staining platform to minimize variability and reduce manual steps across IHC processes. 

The VENTANA HER2 Dual ISH DNA Probe Cocktail detects HER2 gene amplification using dual‑color technology that allows pathologists to compare HER2 status with hematoxylin and eosin and other gastrointestinal panel markers within the same case, and it also maintains high concordance with HER2 FISH.

The company states that this clearance broadens access to HER2‑targeted therapies for patients with HER2‑positive GEA and notes that until now no tests had been approved to determine HER2 status in esophageal cancer, limiting access to targeted therapy. Already widely used and trusted in breast and gastric cancers, the tests are intended to provide reliable, actionable results that support diagnostic precision across tumor types.

“GEA can be a difficult diagnosis for patients to face, with most cases only being detected once the disease has progressed to an advanced stage. By adding GEA to the approved indications for our widely-available HER2 assay, we expand the patient population eligible for targeted therapy and potentially improve patient outcomes,” said Laura Apitz, Head of Pathology Lab at Roche Diagnostics.