Is lymph node dissection required in pulmonary metastasectomy for colorectal adenocarcinoma?

Background: The aim of this study was to clarify the clinical outcome and significance of mediastinal lymph node dissection (LND) during pulmonary resection of metastases from colorectal adenocarcinoma. Methods: A retrospective chart review was performed. Between April 1985 and December 2009, 518 patients underwent 720 pulmonary metastasectomies for metastatic colorectal adenocarcinoma. Relevant factors were analyzed with the χ² or Fisher exact test and the Mann-Whitney test. Survival and lymph node (LN) recurrence-free period after pulmonary metastasectomy were analyzed with Kaplan-Meier and Cox proportional hazards methods. Results: The overall 5-year and 10-year survival rate after pulmonary metastasectomy were 47.1% and 27.7%, respectively. The only significant prognostic factor for survival after pulmonary metastasectomy was mediastinal LN metastasis (p = 0.047 in univariate and 0.0028 in multivariate analysis); 199 patients did not undergo LND, 279 patients underwent LND that were negative, and 40 patients underwent LND that contained 1 or more positive mediastinal LN for metastases. The sensitivity of positron emission tomographic scan for detecting mediastinal LN metastases was only 35%. Although long-term survivors were present, systematic LND was not a significant factor for prolonged survival (p = 0.26) in the positive LND group. Conclusions: Mediastinal LN metastases are a significant negative prognostic factor for survival after pulmonary metastasectomy for metastatic colorectal cancer. Computed tomography and positron emission tomography based imaging, as well as preoperative carcinoembryonic antigen levels have poor sensitivity for detecting malignant mediastinal LN in this setting. Systematic mediastinal LND should be performed for prognostic purposes during pulmonary metastasectomy for colorectal metastases.