[Investigation of Lateral Lymph Node Dissection for Rectal Cancer in Our Department]

No clear policy has been established in Japan for proper lymph node dissection for rectal cancer. In our department, we examined the frequency of lateral lymph node metastasis, its treatment outcomes, and whether lateral dissection can narrow down necessary cases. In 10 years from 2003 to 2013, 98 cases of lower rectal cancer surgically treated in our department were examined. The clinicopathological factors in these cases were examined, and the risk factors were examined based on their correlation with the presence or absence of lateral lymph node metastasis. Based on the postoperative prognostic analysis, the dissection effect index(metastasis positive rate×5-year survival rate in cases with positive metastases)was also examined. Forty-three lateral lymph node dissections were performed. Cases involving a circumferential resection margin (CRM)of 1mm or less had significantly more lateral lymph node metastases. In the prognostic analysis, the 5-year survival rate of lateral lymph node metastasis-positive cases was 19%, and the dissection effect index was 3.5. It was suggested that CRM-positive patients had a higher risk of lateral lymph node metastasis before surgery. However, considering the results of this study and the results of JCOG0212, the presence or absence of lateral lymph node metastasis may be a prognostic predictor, although the prognostic improvement effect by dissection is considered to be limited.