Validation of limited lymphadenectomy for lower-third gastric cancer based on depth of tumour invasion

Background: This study aimed to determine the appropriate extent of lymph node (LN) dissection in gastric cancer by analysing LN metastasis patterns from prospectively collected topographical data on nodal status at Seoul National University Hospital, Korea. Methods: The metastasis rate for each LN station was analysed according to the depth of tumour invasion in patients with primary lower-third gastric cancer who underwent curative gastrectomy. The Maruyama Index of unresected disease (MI) was calculated using the WinEstimate (R) program with simulation of various extents of LN dissection. Results: LN metastasis in mucosal cancer was rare; 2.6 per cent of patients had a MI of more than 5 with simulation of D1 plus station 7 dissection, whereas 0.9 per cent had a MI above 5 with D1 plus stations 7 and 8a. In submucosal cancer, 3.3 per cent of tumours metastasized to level 2 LN stations outside the range of D1 plus stations 7, 8a and 9. The proportion of patients with a MI above 5 was 9 . 0 per cent with D1 plus stations 7, 8a and 9 dissection. The nodal metastasis rate was higher at level 1 and 2 for muscularis propria or deeper cancers. Conclusion: D1 dissection plus stations 7 and 8a for mucosal cancer, and D2 dissection for cancers of the muscularis propria or deeper seems appropriate. For submucosal cancer, an expanded dissection to the D2 level should be considered to ensure complete removal of metastatic LNs.