## Adjuvant Chemotherapy in Gastric Cancer **Key Point:** 5-FU + Cisplatin is the standard adjuvant regimen for resected gastric cancer, particularly in stage IB–III disease, based on the MAGIC trial and subsequent guidelines. ### Evidence Base The **MAGIC trial** (2006) demonstrated that perioperative ECF (Epirubicin–Cisplatin–5-FU) or ECX (Epirubicin–Cisplatin–Capecitabine) improved overall survival in resectable gastric cancer. In India and most resource-limited settings, **5-FU + Cisplatin** is the preferred adjuvant doublet because: 1. **Proven survival benefit** — OS improvement of ~13% at 5 years in stage II–III disease 2. **Cost-effectiveness** — Cisplatin and 5-FU are affordable and widely available 3. **Tolerability** — Manageable toxicity profile in the adjuvant setting 4. **Guideline consensus** — Endorsed by NCCN, ESMO, and Indian surgical societies ### Timing & Dosing - **Initiation:** Within 6–8 weeks of curative resection (R0) - **Duration:** Typically 6 cycles of 21-day cycles - **Regimen:** Cisplatin 75–100 mg/m² IV day 1 + 5-FU 750 mg/m² IV daily × 5 days ### Stage-Specific Application | Stage | Adjuvant Chemotherapy | Indication | |-------|----------------------|------------| | IA (T1a, N0) | Observation | No survival benefit proven | | IB (T1b–T2, N0) | Consider 5-FU + Cisplatin | Borderline; often given | | II–III | 5-FU + Cisplatin (standard) | Clear OS benefit | | IV (M1) | Palliative chemotherapy | Not adjuvant | **High-Yield:** Early T1b gastric cancers (submucosa involved) have ~15–20% risk of lymph node metastasis; adjuvant chemotherapy is increasingly recommended even in node-negative T1b cases to prevent occult micrometastatic disease. ### Role of Trastuzumab - **HER2 testing** is mandatory in gastric cancer (IHC 3+ or FISH+) - **Trastuzumab** is added to chemotherapy in HER2-positive advanced disease (Trastuzumab for Gastric Cancer [ToGA] trial) - In the adjuvant setting, trastuzumab is **not standard monotherapy** — it is combined with chemotherapy only if HER2+ and stage III **Clinical Pearl:** Always perform HER2 testing on the resected specimen. If HER2-positive and stage III, consider 5-FU + Cisplatin + Trastuzumab; if HER2-negative, 5-FU + Cisplatin alone is sufficient. ### Why Not Other Options? - **Paclitaxel monotherapy:** No survival benefit as adjuvant monotherapy; used only in combination (e.g., docetaxel + 5-FU + cisplatin in advanced disease) - **Irinotecan + Cetuximab:** Role in metastatic disease only; not standard adjuvant - **Trastuzumab alone:** Requires HER2 positivity AND must be combined with chemotherapy, not given as monotherapy
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