Management of Gastric Cancer: Localized and Advanced Disease
For localized gastric cancer (stage I-III), perioperative chemotherapy combined with D2 gastrectomy is the standard of care, while advanced/metastatic disease (stage IV) requires systemic chemotherapy with targeted therapy or immunotherapy based on biomarker status, prioritizing fluoropyrimidine-platinum doublets plus checkpoint inhibitors for PD-L1 CPS ≥1 or trastuzumab for HER2-positive tumors 1, 2.
Localized Disease (Stage I-III): Algorithmic Approach
Very Early Disease (T1a)
Endoscopic resection is appropriate when all five criteria are met 1:
- Confined to mucosa (T1a)
- Well-differentiated (G1-2)
- Non-ulcerated
- Size < 2 cm
- No lymphovascular invasion
If any criterion is violated, proceed to surgical resection.
Stage IB-III: Multimodality Treatment
The preferred approach is perioperative chemotherapy (neoadjuvant + adjuvant) combined with surgery 1, 2:
Preoperative Phase:
- Triplet regimen: fluoropyrimidine + platinum (oxaliplatin preferred over cisplatin for lower toxicity) + docetaxel 1, 2
- Duration: 2-3 months preoperatively
- Advantages: tumor downsizing, improved R0 resection rates, better tolerance than adjuvant-only therapy
Surgical Phase:
- D2 lymphadenectomy is mandatory 1, 2
- Subtotal gastrectomy if ≥3 cm proximal margin achievable (5 cm for diffuse/poorly cohesive subtypes) 1
- Diagnostic laparoscopy with peritoneal washings recommended before surgery to exclude occult peritoneal disease 1
Postoperative Phase:
- Continue same chemotherapy regimen for 2-3 months 1
- If perioperative therapy not given: adjuvant chemotherapy for 6 months (fluoropyrimidine + oxaliplatin or docetaxel doublet) 1
- Alternative for inadequate lymphadenectomy (<D2): postoperative chemoradiation 2
Critical Pitfall: Adjuvant-only chemotherapy is less well tolerated and less effective than perioperative approaches—always attempt neoadjuvant therapy when feasible 1.
Advanced/Metastatic Disease (Stage IV): Biomarker-Driven Strategy
First-Line Therapy Algorithm
Step 1: Assess Biomarker Status
- HER2 overexpression (IHC/FISH)
- PD-L1 CPS (combined positive score)
- MSI-H/dMMR status
Step 2: Select Regimen Based on Biomarkers
For HER2-Positive Disease:
- Preferred: Fluoropyrimidine (5-FU or capecitabine) + oxaliplatin + trastuzumab + pembrolizumab (if PD-L1 CPS ≥1) 2
- Alternative: Same regimen with cisplatin instead of oxaliplatin 2
- This is Category 1 evidence for the quadruplet regimen in PD-L1 CPS ≥1 patients
For HER2-Negative Disease:
- If PD-L1 CPS ≥5: Fluoropyrimidine + oxaliplatin + nivolumab (Category 1) 2
- If PD-L1 CPS 1-4: Fluoropyrimidine + oxaliplatin + pembrolizumab 2
- If PD-L1 CPS <1: Fluoropyrimidine + platinum doublet alone
For MSI-H/dMMR Tumors:
- Immunotherapy should be first-choice when available, regardless of other biomarkers 3
- These tumors show exceptional responses to checkpoint inhibitors
Key Principle: Two-drug cytotoxic regimens are preferred over three-drug regimens due to lower toxicity; reserve triplets for medically fit patients with excellent performance status (ECOG 0-1) 2.
Second-Line and Beyond
Second-Line Options:
- Ramucirumab (anti-VEGFR2) + paclitaxel 3
- This combination has demonstrated survival benefit in randomized trials
Performance Status Considerations:
- Systemic therapy appropriate for KPS ≥60% or ECOG PS ≤2 2
- Below these thresholds, focus on best supportive care
Emerging Role of Surgery in Stage IV
Highly Selected Oligometastatic Disease:
- Cytoreductive surgery + HIPEC may benefit patients with limited peritoneal carcinomatosis (Peritoneal Carcinomatosis Index ≤6), no distant metastases, good response to chemotherapy, and ECOG 0-1 4
- Resection of isolated non-peritoneal metastases (hepatic, pulmonary) can be considered in specific contexts after excellent response to systemic therapy 4
- Critical caveat: This remains investigational and requires prospective trial validation
Important Nuances and Pitfalls
Oxaliplatin vs. Cisplatin: Both guidelines explicitly prefer oxaliplatin due to significantly lower toxicity profile without compromising efficacy 2.
Geographic Variations: Asian guidelines emphasize S-1 (tegafur-gimeracil-oteracil) based regimens, while Western guidelines focus on fluoropyrimidine-platinum combinations 5, 6. The evidence presented here prioritizes Western approaches (ESMO, NCCN) as most applicable globally.
Biomarker Testing Timing: HER2 and PD-L1 testing must occur at initial diagnosis via endoscopic biopsy to guide first-line therapy selection 1.
R1 Resection Management: For positive margins after surgery, adjuvant chemoradiation may be considered individually but is not standard practice 1.
Multidisciplinary Planning: Treatment decisions must involve surgeons, medical oncologists, radiation oncologists, gastroenterologists, radiologists, and pathologists before initiating any therapy 1.