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Background: The ratio of metastatic to total retrieved nodes, defined Lymph Node Ratio (LNR), has shown a better prognostic significance in several gastrointestinal cancers compared to the absolute number of positive lymph nodes. The aim of this study was to assess the value of LNR on long-term outcome of patients submitted to colorectal surgery for malignancies.

Methods: Clinical and pathologic data of patients underwent colorectal surgery for resectable cancer at our Department of Surgical Sciences were routinely and prospectively inserted in a database between January 2003 and August 2011 . We reviewed the total number of lymph nodes retrieved in the surgical specimen and the number of lymphatic metastasis. The value of the LNR was compared with the long term outcome for each patients, and the prognostic significance of LNR evaluated using the Kaplan-Meier survival curve and the log-rank test.

Results: From an overall database of 1004 patients we selected two hundred and thirty patients
(51.3% male, 48.6 % female) that fulfilled the study criteria. The mean age of the study group was 68.4 ± 10.5 years. The type of surgery performed were right colectomy in 72 patients (31.3%), left colectomy in 73 patients (31.7%), anterior resection or miles procedure in 79 patients (34.3%) and other procedures in 6 patients ( 2.6%). Ten patients (4.3%) were T1 staged , 30 (13.1%) were T2, 167 (72.6%) were T3 and 23 (10%) were T4. The mean number of lymph node retrieved were 13.6 ± 6.9 and 89 patients (38.7%) were node positive with a mean metastatic lymph node number of 1,4 ± 2.7. Since LNR increase as a function of metastatic lymph node number we found that a LNR between 0.1 and 0.2 compared to LNR major than 0.2 has a significant difference in predicting the long term outcome of these patients ( p= 0.04).

Conclusion: After colorectal cancer surgery the LNR is an accurate prognostic factor in node-positive patients in long term overall survival and disease free survival.