Effects of mediastinal lymph node dissection in colorectal cancer-related pulmonary metastasectomy

Background: The benefits of mediastinal lymph node dissection (MLND) in colorectal cancer-related pulmonary metastasectomy (PM) have been poorly reported. This study aimed to determine whether MLND affects survival in patients undergoing PM and to identify the prognostic factors for survival. Methods: We retrospectively reviewed 275 patients who had undergone colorectal cancer-related PM from January 2010 to December 2016. MLND was defined as the resection of at least six mediastinal lymph node stations according to the International Association for the Study of Lung Cancer criteria (N1, ≥3 stations; N2, ≥3 stations). The propensity score matching method was used to reduce bias. Results: Thirty-three (12%) patients underwent MLND, and 13 (4.7%) patients had mediastinal lymph node involvement. This study showed no difference in 5-year overall survival (no MLND, 52.7% vs. MLND, 53.5%; p = 0.81). On multivariable analysis, negative prognostic factors for overall survival were preoperative carcinoembryonic antigen (CEA) level (p < 0.001), a higher number of metastatic nodules (p < 0.001), metastatic nodule size ≥2 cm (p < 0.001), and lymph node involvement (p = 0.006). Conclusions: Mediastinal lymph node involvement, preoperative CEA level, higher metastatic nodule number, and nodule size negatively affected survival whereas MLND in PM was not associated with survival.