What is the best investigation to stage the primary (T) tumor in a patient with confirmed gastric antrum adenocarcinoma presenting with weight loss and dyspeptic symptoms?

T-Staging of Gastric Antrum Adenocarcinoma

Endoscopic ultrasound (EUS) is the best investigation for T-staging of gastric adenocarcinoma, though its accuracy is notably limited in antral tumors.

Primary Staging Modality

Contrast-enhanced CT of the thorax, abdomen, and pelvis should be performed first as the foundational staging investigation for all gastric cancer patients 1, 2. CT provides essential information about distant metastases, regional lymphadenopathy, and overall disease extent 1.

Role of Endoscopic Ultrasound

EUS is helpful for determining tumor depth (T-stage) and proximal/distal extent, but multiple high-quality guidelines explicitly state that EUS is less useful in antral tumors 1. This is a critical caveat for your specific case.

EUS Performance Data

• Overall T-staging accuracy ranges from 64-68% across studies 3, 4, 5
• Accuracy is highest for T3 tumors (75%) but drops significantly for other stages 4
• EUS tends to overstage gastric cancer (24.4% overstaging rate) due to perifocal inflammation mimicking deeper invasion 5
• Agreement between EUS and final pathology is only fair (kappa = 0.28) for T-stage 6

When EUS Adds Value

Despite limitations in antral location, EUS may improve diagnostic accuracy particularly for discriminating:

• T1a (mucosal) from T1b (submucosal) disease—sensitivity 87%, specificity 75% 3
• T1-T2 (superficial) from T3-T4 (advanced) disease—sensitivity 86%, specificity 90% 3
• Early gastric cancer requiring endoscopic vs. surgical treatment 1

EUS is formally indicated when selecting patients for endoscopic treatment but is not strictly necessary in obviously advanced forms 1.

Complementary Staging Investigations

Staging Laparoscopy

Laparoscopy with peritoneal washings is recommended for all stage IB-III gastric cancers to exclude occult peritoneal metastases missed by imaging in 20-30% of cases 1, 2.

PET Imaging

PET may upstage patients but can be falsely negative in mucinous and diffuse tumors, limiting utility 1, 2.

Answer to Multiple Choice Question

The correct answer is A - Endoscopic US, as it remains the best available modality specifically for T-staging despite reduced accuracy in antral locations 1, 2.

• Option B (Abdominal US) is not a standard staging modality for gastric cancer T-stage 2
• Option C (Nuclear scan) refers to PET, which is useful for N/M staging but not optimal for T-stage 1
• Option D (Gastrographic study) is outdated and not recommended in modern guidelines 2

Critical Clinical Pitfalls

• Do not rely on EUS alone for antral tumors—combine with high-quality CT findings 1, 6
• Circumferential lesions ≥1/2 stomach, signet ring cell histology, and Borrmann IV type are associated with higher EUS understaging rates 4
• Perifocal inflammation causes overstaging by mimicking deeper wall invasion 5
• Absence of serosa in certain gastric areas leads to T-stage misclassification 5

Practical Algorithm

1. Obtain contrast-enhanced CT thorax/abdomen/pelvis first 1, 2
2. Perform EUS for T-stage assessment despite antral location limitations 1
3. Add staging laparoscopy if stage IB-III to exclude peritoneal disease 1, 2
4. Interpret EUS cautiously in antral tumors—consider CT findings and clinical context when discordant 1, 6