The aims of this study are to identify the natural course of inferior mesenteric artery (IMA) lymph node metastasis, and to evaluate the prognostic impact of IMA lymph node metastasis in the sigmoid colon and rectal cancer.

From our prospectively collected database, a total of 625 patients who underwent resection with curative intent for stage III adenocarcinoma of the sigmoid colon and rectal cancer between June 1995 and June 2007 were selected. Patients were divided into the IMA-positive group (n = 33) and the IMA-negative group (n = 592) according to IMA lymph node metastasis status. Clinicopathological features, recurrence patterns, and 5-year disease-free survival rates were compared between the two groups.

Following curative resection, 5-year disease-free survival rate was 31.9% in the IMA-positive group and 69.4% in the IMA-negative group (p < 0.001). Cox regression analysis revealed that rectal cancer, pathologic stage, and presence of IMA lymph node metastasis were independently associated with disease-free survival. Systemic recurrence rate was significantly higher in the IMA-positive group than in the IMA-negative group (48.5 vs. 20.8%, respectively, p = 0.001). Para-aortic nodal recurrence showed significant association with presence of IMA lymph node metastasis on multivariate analysis (hazard ratio 11.8; 95% confidence interval 2.7-52.2, p = 0.001).

Presence of IMA lymph node metastasis should be considered as a predictive factor for high systemic recurrence, and should be treated and followed up with caution for para-aortic nodal recurrence.