Initial Workup for Suspected Gastric Cancer
All patients with suspected gastric cancer require esophagogastroduodenoscopy (EGD) with multiple biopsies (5-8 samples), CT chest/abdomen/pelvis with oral and IV contrast, complete blood count, comprehensive metabolic panel, and universal MSI/MMR testing 1, 2.
Essential Initial Diagnostic Studies
Endoscopic Evaluation
- EGD with biopsy is the gold standard for diagnosis 2
- Obtain 5-8 biopsies to ensure adequate tissue for histological and molecular analysis, particularly in ulcerated lesions 2
- Consider narrow-band imaging or chromoendoscopy with magnification for detailed mucosal surface evaluation 2
Laboratory Testing
- CBC (to assess for anemia from chronic bleeding)
- Comprehensive chemistry profile 1
Cross-Sectional Imaging
- CT chest/abdomen/pelvis with oral AND intravenous contrast is mandatory 1
- This provides initial staging information and identifies metastatic disease
Risk-Stratified Additional Workup
If Early-Stage Disease is Suspected
- Endoscopic ultrasound (EUS) is preferred to differentiate early versus locally advanced disease 1
- Endoscopic resection (ER) is essential for accurate staging of T1a or T1b cancers and may be both diagnostic and therapeutic 1
If Locally Advanced or Metastatic Disease
- FDG-PET/CT from skull base to mid-thigh is recommended 1
- Note: PET/CT may not be appropriate for T1 disease 1
- Biopsy metastatic sites as clinically indicated 1
Molecular and Biomarker Testing
Universal Testing (All Patients)
- MSI status by PCR/NGS or MMR status by IHC 1
If Advanced/Metastatic Disease Documented or Suspected
Specialized Assessments
For Esophagogastric Junction Tumors
- Assess Siewert tumor type as part of initial workup 1
Supportive Care Evaluations
- Nutritional assessment and counseling 1
- Smoking cessation advice, counseling, and pharmacotherapy if indicated 1
- Screen for family history of gastric cancer 1
- If familial cancer syndrome suspected, refer to genetics 2
Common Pitfalls to Avoid
Do not rely on a single biopsy - inadequate sampling is a major cause of false-negative results. The requirement for 5-8 biopsies addresses this directly 2.
Do not skip EUS in suspected early disease - accurate T-staging is critical for determining whether endoscopic resection alone is curative versus requiring surgery 1.
Do not delay molecular testing - HER2, PD-L1, CLDN18.2, and MSI/MMR status directly impact first-line treatment decisions in advanced disease and should be obtained at diagnosis, not after progression 1.
Do not order PET/CT for clearly early T1 disease - this adds cost without changing management 1.