HER2 testing in gastric cancer: a practical approach

Area of Science:

• Oncology
• Molecular Diagnostics
• Gastrointestinal Cancer Research

Background:

• Trastuzumab is approved for HER2-positive metastatic gastric and gastro-esophageal junction adenocarcinoma.
• Accurate HER2 testing is vital for patient selection, similar to breast cancer treatment.
• Gastric cancer presents unique HER2 testing challenges, including heterogeneity and incomplete staining.

Purpose of the Study:

• To provide updated, practical guidance on HER2 testing and scoring in gastric cancer.
• To ensure accurate identification of patients eligible for trastuzumab therapy.
• To standardize HER2 testing protocols specific to gastric cancer's biological characteristics.

Main Methods:

• Recommends immunohistochemistry (IHC) as the primary HER2 testing method.
• Specifies fluorescence in situ hybridization (FISH) or silver in situ hybridization (SISH) for retesting IHC 2+ samples.
• Advocates for bright-field methodologies over fluorescent ones for better detection of heterogeneous staining.

Main Results:

• Gastric cancer requires specific HER2 testing protocols due to tumor biology differences from breast cancer.
• Adherence to standardized protocols is imperative for reliable HER2 assessment.
• Expert panel consensus provides up-to-date practical guidance reflecting regulatory approvals.

Conclusions:

• Standardized HER2 testing, including specific training, is essential for gastric cancer.
• Consistent and accurate HER2 testing ensures appropriate patient selection for trastuzumab.
• Implementation of these guidelines is anticipated to improve treatment outcomes for HER2-positive gastric cancer patients.