FGFR2b in Gastric Cancer: Translating a Therapeutic Target into a Reliable Biomarker

Area of Science:

• Oncology
• Molecular Biology
• Biomarker Discovery

Background:

• Fibroblast growth factor receptor 2b (FGFR2b) is a critical therapeutic target in gastric and gastroesophageal junction cancers.
• FGFR2b-directed antibody therapies are under clinical development, necessitating accurate patient selection.

Purpose of the Study:

• To critically evaluate the reliability of FGFR2b as a biomarker for guiding gastric cancer therapy.
• To explore the complexities of FGFR2b assessment beyond simple protein detection.

Main Methods:

• Review of biological basis for FGFR2b targeting.
• Analysis of factors contributing to variability in reported FGFR2b positivity rates.
• Examination of clinical evidence for FGFR2b-targeted therapies.

Main Results:

• FGFR2b assessment by immunohistochemistry can be confounded by staining intensity, cell percentage, sample type, and distribution.
• FGFR2b protein expression, gene amplification, and pathway dependency are distinct but related.
• Intratumoral heterogeneity and inter-lesion variability impact biomarker reliability.

Conclusions:

• Successful FGFR2b-directed therapy relies on standardized testing, careful reporting, and reassessment of changing tumor biology.
• Interpreting FGFR2b requires considering its expression, representativeness, and biological relevance for guiding treatment.
• FGFR2b serves as a model for developing protein biomarkers as clinically interpreted variables in gastric cancer.