Infrapyloric Lymph Node Metastasis in Middle/Lower Gastric Cancer: Key Findings from a Multicenter Prospective Study
Gastric cancer is one of the most common cancers in China, with most cases arising in the middle or lower part of the stomach. For these patients, metastasis to the infrapyloric lymph node (called “No. 6” in surgical classification) is a critical concern—this node sits near the pylorus (the stomach’s lower opening to the small intestine) and is often a first stop for cancer spread. But until now, many studies on No. 6 metastasis were retrospective (looking back at past cases) or lacked strict surgical quality control, leaving gaps in how doctors guide treatment.
A new analysis of the IPA-Origin study—a prospective, multicenter observational trial (ClinicalTrials.gov: NCT03071237) with 34 Chinese gastrointestinal surgery centers—offers clearer insights into who is at risk for No. 6 lymph node metastasis. Led by researchers from institutions including Shanghai Ruijin Hospital, Peking University Cancer Hospital, and Renji Hospital, the study focused on 120 patients who underwent distal gastrectomy (partial stomach removal) and had detailed data on No. 6 lymph nodes and the distance between their tumor and the pylorus (called the distal resection margin, or DRM).
What the Study Found
Overall, 22.5% of patients (27 out of 120) had No. 6 lymph node metastasis. The risk was higher in advanced-stage cancers: 30.8% of patients with T2–T4a tumors (locally advanced) had metastasis, compared to 12.7% of those with early-stage T1 tumors.
When researchers looked for factors linked to metastasis, two stood out as independent risks—meaning they mattered even when other variables (like age or gender) were considered:
- Tumor size ≥2 cm: Patients with larger tumors were 8 times more likely to have No. 6 metastasis than those with tumors smaller than 2 cm.
- DRM ≤3 cm: If the tumor was within 3 cm of the pylorus, patients were nearly 4 times more likely to have metastasis than those with tumors farther away.
Other factors—like advanced tumor stage, nerve/vessel invasion—were linked to higher risk in initial analysis but didn’t hold up as independent drivers once size and DRM were accounted for.
Why This Matters for Patients and Doctors
Lymph node dissection is a cornerstone of gastric cancer surgery: removing affected nodes improves survival and guides post-op treatment. For middle/lower gastric cancer, the No. 6 node is often targeted—but not all patients need it removed. This study helps doctors identify who needs thorough No. 6 dissection:
- Even early-stage tumors (T1) can metastasize to No. 6 if they’re large (≥2 cm) or close to the pylorus (DRM ≤3 cm). For these cases, pylorus-preserving gastrectomy (which spares the pylorus to preserve digestion) may not be safe—complete No. 6 dissection is better.
- For advanced-stage tumors, the higher metastasis rate (30.8%) reinforces that No. 6 dissection is essential.
The IPA-Origin study’s strength lies in its prospective design (enrolling patients before surgery) and strict quality control—surgeons recorded photos/videos of the No. 6 area to ensure accurate node assessment. This addresses gaps in earlier research, where retrospective designs or variable surgical techniques made results less reliable.
Conclusion
For patients with middle/lower gastric cancer, tumor size (≥2 cm) and proximity to the pylorus (≤3 cm) are the biggest red flags for No. 6 lymph node metastasis. Regardless of whether the cancer is early or advanced, doctors should prioritize complete No. 6 lymph node dissection if these factors are present. This could improve survival and reduce the risk of cancer recurrence.
The study, published in the Chinese Medical Journal in 2020, was led by Tasiken Baheti (Shanghai Ruijin Hospital) and Ru-Lin Miao (Peking University Cancer Hospital), with contributions from 21 researchers across China.
doi:10.1097/CM9.0000000000000995
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