A 62-year-old Indian woman undergoes subtotal gastrectomy with D2 lymphadenectomy for T2N2 gastric cancer of the antrum. Intraoperatively, the surgeon notes that the left gastroepiploic vessels are densely adherent to the tumour and cannot be separated without breaching the tumour capsule. The surgeon divides these vessels close to the stomach. Histopathology shows a 4 cm tumour with invasion into the muscularis propria, 8 involved regional lymph nodes, and negative margins (5 cm proximal, 3 cm distal). What is the most likely reason this patient will have poor long-term survival despite R0 resection?

Explanation

## Prognostic Factors in Gastric Cancer After R0 Resection **Key Point:** Despite achieving R0 resection (negative margins), the number of involved lymph nodes (N stage) is the single most powerful independent predictor of survival in gastric cancer. N2 disease (7–15 involved nodes) carries a significantly worse prognosis than N0 or N1. ### TNM Staging and Survival Correlation | N Stage | Involved Nodes | 5-Year Survival (%) | Prognosis | |---------|---|---|---| | N0 | 0 | 60–70 | Good | | N1 | 1–2 | 40–50 | Intermediate | | N2 | 3–6 | 20–30 | Poor | | N3a | 7–15 | 10–15 | Very poor | | N3b | >15 | <5 | Extremely poor | **High-Yield:** In this case, 8 involved nodes = N3a (not N2 by current AJCC 8e classification), which carries a 5-year survival of only 10–15% despite R0 resection. This reflects aggressive tumour biology and high likelihood of occult micrometastases. ### Why N Stage Dominates Prognosis 1. **Nodal involvement reflects tumour aggressiveness:** Extensive lymph node metastases indicate: - High propensity for vascular invasion - Greater likelihood of occult peritoneal or distant micrometastases - More advanced locoregional disease 2. **Systemic disease burden:** Patients with N2–N3 disease have high rates of recurrence (locoregional, peritoneal, hepatic) within 2 years despite R0 surgery. 3. **Adjuvant chemotherapy benefit:** N2–N3 patients derive significant benefit from perioperative chemotherapy (MAGIC trial, AJCC guidelines), but survival remains poor compared to N0–N1 [cite:MAGIC Trial, cite:JCOG0501]. **Clinical Pearl:** The presence of 8 involved nodes in a 4 cm tumour indicates a high tumour burden and aggressive phenotype. Even with complete resection, the risk of occult metastatic disease is substantial. ### Assessment of Margins **Distal margin (3 cm):** For antral tumours, a 3 cm distal margin is acceptable and meets R0 criteria. Japanese guidelines recommend ≥3 cm for antral tumours; proximal margin ≥5 cm is more critical for proximal tumours. This margin is adequate. **Proximal margin (5 cm):** Excellent, well above the 5 cm threshold for antral cancers. ## Why Not the Other Options? **Inadequate distal margin:** A 3 cm distal margin is adequate for antral gastric cancer and meets R0 criteria. The distal margin is not the limiting prognostic factor here. **Division of left gastroepiploic vessels:** While this is a technical concern, the left gastroepiploic nodes (station 4d) are part of D1, not D2. Incomplete D2 dissection would not explain the 8 involved nodes found—these are already resected. The poor prognosis reflects the burden of disease, not incomplete dissection. **Failure to perform total gastrectomy:** Subtotal gastrectomy is appropriate for antral tumours with adequate margins. Total gastrectomy is not mandatory for distal cancers and would not improve survival in this case.