What is the initial management for a patient diagnosed with localized gastric adenocarcinoma?

Initial Management of Localized Gastric Adenocarcinoma

The initial management of localized gastric adenocarcinoma requires multidisciplinary team evaluation followed by either endoscopic resection for very early disease meeting strict criteria, or surgical resection with perioperative chemotherapy for all other resectable disease. 1, 2

Mandatory First Steps

Multidisciplinary Team Discussion

• All cases must be discussed in a multidisciplinary team before any treatment decision, including surgeons, medical and radiation oncologists, gastroenterologists, radiologists, and pathologists. 1, 2
• When local expertise is unavailable, refer patients to an expert center before proceeding. 1

Complete Staging Workup

Before determining treatment approach, obtain: 1, 2

• Full blood count to assess for iron deficiency anemia
• Renal and liver function tests to determine appropriate therapeutic options
• Contrast-enhanced CT of thorax and abdomen for staging
• Endoscopic ultrasound (EUS) for accurate T and N staging in potentially operable tumors
• Diagnostic laparoscopy with peritoneal washings to exclude occult peritoneal metastases
• HER2 testing on biopsy specimens for molecular biomarker assessment
• Nutritional status assessment to detect dietary deficiencies

Treatment Algorithm Based on Disease Characteristics

Very Early Disease: Endoscopic Resection Criteria

Endoscopic resection (ESD preferred over EMR for lesions >10mm) is curative ONLY when ALL of the following criteria are met: 1

1. Confined to mucosa (T1a)
2. Well or moderately differentiated (G1-2)
3. Non-ulcerated
4. <2 cm in diameter

Expanded criteria may be considered (but require expert evaluation) if no more than two of the following are present: 1

• Well/moderately differentiated intramucosal adenocarcinoma of any size without ulceration
• Well/moderately differentiated intramucosal adenocarcinoma ≤3.0 cm if ulcerated
• Well/moderately differentiated submucosal adenocarcinoma <3.0 cm with superficial submucosal invasion (Sm1; <500 μm)
• Poorly differentiated intramucosal adenocarcinoma ≤2.0 cm

Critical caveat: These criteria apply to intestinal-type gastric cancer only. Diffuse-type adenocarcinoma carries worse prognosis and requires surgical resection. 1

High-Risk Features Requiring Surgery After Endoscopic Resection

If any of the following are found on pathology after endoscopic resection, proceed immediately to surgical gastrectomy: 1

• Poorly differentiated submucosal cancer (any depth)
• Signet ring cell histology
• Lymphovascular invasion present
• Submucosal invasion ≥500 μm from muscularis mucosae

These features indicate lymph node metastasis risk of 6.7-22.7%, making endoscopic resection inadequate. 1

Stage IB and Above: Surgical Resection with Perioperative Chemotherapy

For all resectable gastric adenocarcinoma beyond very early disease, the standard approach is perioperative chemotherapy combined with surgical resection. 1, 2

Perioperative Chemotherapy Protocol

• Preferred regimen: Triplet chemotherapy with fluoropyrimidine + platinum compound + docetaxel when possible 1, 2
• Duration: 2-3 months preoperatively, then surgery, then 2-3 months postoperatively 1
• Rationale: Neoadjuvant therapy leads to tumor downsizing for more curative resections and is better tolerated than adjuvant-only approaches 1

Surgical Resection Standards

• D2 lymphadenectomy (removal of perigastric and second-tier lymph nodes) is the standard surgical approach 1
• Minimum 15 lymph nodes must be harvested for adequate staging 3
• Resection margins: 3 cm macroscopic proximal margin for intestinal-type; 5 cm for diffuse-type adenocarcinoma 1
• R0 resection (microscopically negative margins) is the ultimate surgical goal 4, 5

Alternative: Adjuvant-Only Chemotherapy

If surgery was performed without preoperative chemotherapy (not preferred), give adjuvant chemotherapy: 1, 2

• Doublet regimen: Fluoropyrimidine + oxaliplatin OR fluoropyrimidine + docetaxel
• Duration: 6 months total
• Important exception: For MSI-H gastric cancers, adjuvant chemotherapy cannot be recommended 1

Post-Endoscopic Resection Surveillance

After curative endoscopic resection, the recurrence risk is 10-20%, requiring structured surveillance: 1

• First follow-up endoscopy at 6 months after resection 1
• If negative, annual endoscopy thereafter 1
• Most recurrences occur within the first year, making early surveillance critical 1

Common Pitfalls to Avoid

• Do not attempt endoscopic resection for diffuse-type gastric cancer – these require upfront surgery regardless of size or depth 1
• Do not skip laparoscopy for clinical stage IB-III disease – occult peritoneal metastases change management in 10-20% of cases 1
• Do not proceed with surgery before MDT discussion – treatment decisions require multidisciplinary input for optimal outcomes 1, 2
• Do not accept inadequate lymph node harvest – fewer than 15 nodes indicates inadequate staging 3
• Do not use endoscopic resection if any high-risk pathologic features are present – lymph node metastasis risk becomes unacceptably high 1