Japanese D3 Lymph Node Dissection in Low Rectal Cancer with Inferior Mesenteric Lymph Node Metastases

There is currently no consensus on the significance of Japanese D3 lymph node dissection in low rectal cancer with inferior mesenteric lymph node (IMLN) metastasis. This is partly because, despite a number of studies on the subject, cases of IMLN metastasis are relatively rare, and there are few cases of curative resection because of metastasis to other organs. A retrospective study involving a large number of patients was conducted. The subjects were 2,743 patients registered in the national registry of the Japanese Society for Cancer of the Colon and Rectum. The data were analyzed for (1) prognostic factors for IMLN metastasis, and (2) outcomes in R0 cases with IMLN metastasis. In the control group, 67 patients (2.7 %) were considered positive for IMLN metastasis. The outcomes in the 35 R0 cases with IMLN metastasis were 50.8 % for 5-year relapse-free survival (RFS) and 61.9 % for 5-year overall survival (OS), which were each better than for R1+R2 cases (5-year RFS 16.1 %, p = 0.0001; 5-year OS 26.7 %, p = 0.0002). The outcomes for R0 cases (total metastatic lymph nodes a parts per thousand yen7) with IMLN metastasis (5-year RFS 53.9 %, 5-year OS 68.8 %) did not differ significantly from those for IMLN(-) cases (5-year RFS 54.6 %, 5-year OS 57.1 %) (RFS: p = 0.9515, OS: p = 0.4621). It was confirmed that cases of IMLN metastasis in low rectal cancer tend to have a large total number of metastatic lymph nodes, but if curative resection can be performed, a good prognosis can be expected. These results demonstrate the value of radical Japanese D3 lymph node dissection in low rectal cancer with IMLN metastasis.