Metastatic lymph node ratio in stage III rectal carcinoma is a valuable prognostic factor even with less than 12 lymph nodes retrieved: a prospective study.

BACKGROUND The aim of this study was to assess the prognostic value of metastatic lymph node (LN) ratio (MLNR) in stage III rectal cancer and whether this prognostic value remains significant when <12 LNs are retrieved. METHODS This prospective study included 115 patients with stage III rectal cancer from 2006 to 2010. All patients underwent neoadjuvant long-course chemoradiation, curative resection, and postoperative adjuvant therapy (5-fluorouracil and leucovorin). Data collected included demographics, tumor pathology, tumor-node-metastasis staging, number of LNs retrieved, MLNR, recurrence, and mortality. RESULTS The mean number of examined LNs was 12.1, and the mean number of metastatic LNs was 3.5 (range, 1 to 19). The mean MLNR was .37 (range, 0 to 1.00). The mean duration of follow-up was 37 months (range, 24 to 63). Forty patients died during the follow-up period (overall mortality, 34.8%), only 31 because of cancer (cancer-specific mortality, 27%). Univariate analysis revealed that ypN stage, lymphovascular invasion, and follow-up duration were significantly associated with increased recurrence and decreased survival. Number of positive nodes and ypT stage significantly affected recurrence, with no effect on overall survival. Multivariate analysis proved that MLNR was the only independent risk factor for both mortality and recurrence. Prognostic capability was not affected by having <12 nodes retrieved. The best sensitivity and specificity of MLNR as a prognostic factor for both tumor recurrence and overall survival were achieved at a cutoff value of .375. CONCLUSIONS MLNR is an independent prognostic factor for recurrence and survival after the resection of stage III rectal cancer, with high sensitivity and specificity in patients who received neoadjuvant chemoradiation and postoperative chemotherapy. The total number of LN retrieved did not affect the prognostic value of MLNR even if <12.