Ratio of Metastatic to Resected Lymph Nodes as a Prognostic Factor in Node-Positive Colorectal Cancer

Background. This study was designed to assess the prognostic value of the ratio of metastatic to resected lymph nodes (lymph node ratio [LNR]) in patients with node-positive colorectal cancer (CRC). Methods. From May 1998 to December 2007, data from a total of 514 patients who underwent curative surgery for CRC with proven lymph node metastases were analyzed. Patients were categorized into four groups on the basis of quartiles: LNR1 (<0.09), LNR2 (between 0.09 and 0.18), LNR3 (>0.18 and <0.34), and LNR4 (>= 0.34). Results. The median numbers of resected and metastatic nodes were 14 (range, 2-67) and 2 (range, 1-31), respectively. With a median follow-up period of 48.5 months, the 5-year overall survival rates of patients with LNR1, LNR2, LNR3, and LNR4 were 79, 72, 62, and 55%, respectively (P < 0.001); the 5-year disease-free survival rates of patients with LNR1, LNR2, LNR3, and LNR4 were 73, 67, 54, and 42%, respectively (P < 0.001). In the multivariate analysis, the LNR was an independent prognostic factor for both overall (P = 0.012) and disease-free survival (P -= 0.009), as were pT and pN category. LNR remained statistically significant both in patients with <12 and with >12 nodes retrieved. Conclusions. In addition to the conventional pT and pN categories. the LNR was a predictor of both the overall and disease-free survival in patients with node-positive CRC. It may compensate for an inadequate lymph node dissection in surgery for CRC.