Which diagnostic method can detect stomach cancer earlier, Computed Tomography (CT) scans, Positron Emission Tomography (PET) scans, or endoscopy with biopsy?

Endoscopy with Biopsy Detects Stomach Cancer Earliest

Endoscopy with biopsy is the gold standard for early detection of gastric cancer and significantly outperforms both CT and PET scans for identifying early-stage disease. 1

Why Endoscopy is Superior for Early Detection

Direct Visualization and Tissue Diagnosis

• Endoscopic examination with forceps biopsies is the gold standard method for diagnosing gastric cancer, allowing direct visualization of mucosal abnormalities that are invisible to cross-sectional imaging 1
• Multiple biopsies (5-8) should be obtained to provide adequate tissue for histological diagnosis, particularly in ulcerated lesions 1
• Endoscopic resection (ER) is essential for accurate staging of early-stage cancers (T1a or T1b) and can best diagnose early-stage cancers while potentially being therapeutic 1

Enhanced Detection Techniques

• Narrow-band imaging or chromoendoscopy combined with magnifying endoscopy can evaluate detailed mucosal surface characteristics that reveal early cancerous changes 1, 2
• Magnifying narrow-band imaging (M-NBI) with the 'vessel plus surface classification' system has proven very useful for detecting flat or small gastric cancers that conventional white-light imaging may miss 2
• Endoscopic ultrasound (EUS) is recommended if early-stage disease is suspected, as it can accurately distinguish T1a from T1b cancers with 87% sensitivity and 75% specificity 1

Why CT and PET Fail at Early Detection

CT Scan Limitations

• CT scanning has an overall accuracy of only 43-82% for measuring depth of invasion and is limited for early-stage disease 1
• CT cannot reliably detect mucosal or submucosal cancers (T1 lesions) that are curable with endoscopic resection 1
• While CT is useful for staging locally advanced disease and detecting metastases, it misses the early cancers that have the best prognosis 1, 3

PET Scan Limitations

• FDG-PET has lower accuracy for gastric cancer because of low FDG uptake in diffuse and mucinous tumor types, which are common in gastric cancer 1
• PET has been shown to fail in detecting early stages (T1 and T2) of gastric cancer 1
• PET has significantly lower sensitivity compared with CT for detecting local lymph node involvement (56% vs 78%) 1
• FDG-PET/CT is not appropriate for T1 disease and should only be used for locally advanced or metastatic disease 1

Evidence from Screening Programs

Population-Level Data

• In Japan and South Korea, where population-based endoscopic screening is performed widely, early detection often results in improved outcomes 1
• These endoscopy-based screening programs have resulted in higher detection rates of early-stage gastric cancer with substantially reduced mortality 1
• A case-control study in Japan reported a 30% reduction in gastric cancer mortality when screening was undertaken via endoscopy 4

Comparative Performance

• Endoscopic screening for gastric cancer exhibited higher sensitivity and specificity than radiographic screening 4
• False-negative rates for endoscopy are remarkably low at 0% within 12 months when adequate biopsies are performed 5
• Most cost-effectiveness analyses have concluded that endoscopy is more cost-effective than radiographic testing for detecting early gastric cancer 4

Clinical Algorithm for Detection

When to Use Each Modality

1. Primary detection and diagnosis: Esophagogastroduodenoscopy with multiple biopsies (5-8 samples) 1
2. Suspected early-stage disease: Add endoscopic ultrasound to determine if early versus locally advanced disease 1
3. Confirmed early cancer: Endoscopic resection for accurate T-staging and potential cure 1
4. Staging after diagnosis: CT chest/abdomen/pelvis with oral and IV contrast for metastatic workup 1
5. Locally advanced/metastatic disease: FDG-PET/CT from skull base to mid-thigh 1

Critical Pitfall to Avoid

• An inadequate number of biopsies compromises diagnostic accuracy—studies show that significantly fewer biopsies at initial endoscopy (median 2 vs 6) led to missed diagnoses 5
• Never rely on CT or PET alone for initial diagnosis, as they will miss early curable cancers 1
• Population-based endoscopic screening is only recommended in regions with very high incidence of gastric cancer 1