Gastric Cancer Staging
For patients with suspected gastric cancer, perform comprehensive staging with physical examination, complete blood count, liver and renal function tests, endoscopy with biopsy, CT scan of thorax/abdomen/pelvis, endoscopic ultrasound (EUS), and staging laparoscopy with peritoneal washings for all potentially resectable cases. 1
Initial Diagnostic Workup
Tissue diagnosis is mandatory through gastroscopic or surgical biopsy reviewed by an experienced pathologist, with histology reported according to WHO criteria. 1, 2 Obtain 5-8 biopsies to ensure adequate sampling, documenting tumor location, length, circumferential involvement, and degree of obstruction. 3, 4
- Histologic classification: 90% are adenocarcinomas, divided into diffuse (undifferentiated) and intestinal (well-differentiated) types—this distinction impacts prognosis and treatment planning. 1, 2
- Special considerations: Small cell carcinomas must be specifically identified as treatment approaches differ fundamentally. 4
Core Staging Components
Laboratory Assessment
- Complete blood count with differential 1
- Comprehensive metabolic panel including liver function tests (AST, ALT, bilirubin, alkaline phosphatase) and renal function (creatinine, BUN) 1, 4
- Nutritional assessment and ECOG/Karnofsky performance status documentation—critical for determining treatment eligibility. 4
Cross-Sectional Imaging
CT scan of thorax, abdomen, and pelvis with oral and IV contrast is the primary staging modality, providing simultaneous assessment of T-stage, nodal involvement, and distant metastases. 1, 5 Multi-planar reformatted images significantly improve accuracy by avoiding partial volume averaging and optimizing visualization of tumor depth and perigastric infiltration. 5, 6
- Technical considerations: MDCT with isotropic imaging and 3D reconstruction has increased T and N staging accuracy compared to conventional CT. 5, 7
- Limitations: CT has reduced accuracy differentiating T1 from T2 disease, and standardized criteria for N-staging remain controversial. 6
Endoscopic Ultrasound (EUS)
EUS is essential for determining proximal/distal tumor extent and T-stage, particularly valuable for early gastric cancers. 1 However, EUS is less useful for antral tumors and stenotic lesions where the probe cannot traverse. 1, 8
- Optimal use: Most accurate for assessing depth of wall invasion in early cancer (T1-T2 differentiation). 8, 7
- When to skip: If M1 disease already documented, EUS adds minimal value. 4
Staging Laparoscopy
Laparoscopy with or without peritoneal washings is recommended for all patients considered potentially resectable to exclude occult peritoneal metastases. 1, 2 This is particularly critical for T3/T4 adenocarcinomas of the gastroesophageal junction. 4
- Rationale: Prevents unnecessary laparotomy in patients with undetected peritoneal disease—a common site of occult metastases not reliably detected by CT. 1
- Timing: Perform before committing to surgical resection or perioperative chemotherapy. 2
Advanced Imaging Modalities
PET-CT
PET-CT (preferred over PET alone) may upstage patients but can be falsely negative in mucinous and diffuse histologic subtypes. 1 Reserve for cases without evident M1 disease on CT where additional staging information would change management. 4
- Best utility: Detecting and characterizing distant metastases, particularly in equivocal cases. 8
- Limitations: Not reliable for T or N staging; poor sensitivity in signet ring cell and mucinous adenocarcinomas. 1
MRI
While MRI can provide useful staging information, it is not proven superior to MDCT and is not routinely recommended. 8, 7 Diffusion-weighted MRI shows promise but requires further validation. 7, 9
TNM Staging Classification
Stage according to the TNM system and AJCC stage grouping, with the following key definitions: 1, 2
T-Stage (Tumor Depth)
- T1: Invades lamina propria or submucosa
- T2: Invades muscularis propria or subserosa
- T3: Penetrates serosa without invading adjacent structures
- T4: Invades adjacent structures 1, 3
N-Stage (Lymph Node Involvement)
Critical surgical consideration: Minimum of 15 lymph nodes examined (optimally ≥25) required for adequate pathologic staging. 2
M-Stage (Distant Metastasis)
- M0: No distant metastasis
- M1: Distant metastasis present 1
Biomarker Testing
HER2-neu testing is mandatory if metastatic disease is documented or suspected, as it directly impacts treatment selection (trastuzumab eligibility). 4 This should be performed on the initial biopsy specimen to avoid delays in treatment planning.
Multidisciplinary Planning
Multidisciplinary treatment planning is mandatory before initiating therapy, comprising surgeons, medical and radiation oncologists, gastroenterologists, radiologists, and pathologists. 1, 2 This team approach ensures optimal sequencing of surgery, perioperative chemotherapy, and radiation therapy based on accurate clinical staging.
Common Pitfalls to Avoid
- Proceeding to surgery without laparoscopy in potentially resectable cases—misses 20-30% of patients with peritoneal disease. 1
- Relying solely on CT for T-staging in early gastric cancer—EUS is significantly more accurate for T1/T2 differentiation. 8, 7
- Omitting HER2 testing in advanced disease—delays targeted therapy initiation. 4
- Inadequate lymph node harvest (<15 nodes)—results in stage migration and inaccurate prognostication. 2
- Using PET-CT as primary staging in diffuse/signet ring histology—high false-negative rate. 1