Incidence and prognostic significance of lateral lymph node metastasis in patients with advanced low rectal cancer

Background: Lateral lymph node metastases occur in some patients with low rectal cancer and may cause local recurrence after total mesorectal excision. The aims of this study were to identify risk factors for lateral node metastases in patients with pathological turnout (pT) stage 3 or pT4 low rectal adenocarcinoma, and to evaluate the prognostic significance of lateral node metastases. Methods: A retrospective analysis was performed of the outcome of 237 patients with pT3 or pT4 low rectal adenocarcinoma who underwent R0 resection with systematic lateral node dissection. Results: Lateral lymph node metastases were found in 41 patients (17.3 per cent). Increased risk of lateral lymph node metastases was associated with a distal tumour margin close to the anal margin, histological type other than well or moderately differentiated adenocarcinoma, and the presence of mesenteric lymph node metastases. Patients with lateral node metastases had a significantly shorter postoperative survival (5-year survival rate 42 versus 71.6 per cent; P < 0.001) and an increased risk of local recurrence (44 versus 11.7 per cent; P < 0.001) compared with those without lateral node metastases. Conclusion: Tumour site, histological type and the presence of mesenteric lymph node metastasis are factors predicting the risk of lateral node metastasis. The poor prognosis of patients with lateral lymph node metastases after systematic lateral dissection suggests the need for adjuvant therapy.