[Systematic mediastinal lymphadenectomy in surgery for sarcomatous pulmonary metastases]

Systematic lymph node dissection is performed as standard curative resection for non-small cell lung cancer. Its role in lung metastasectomy is unknown. The aim of our study was to find out the frequency of lymph node metastases, the survival of patients with and without lymph node involvement, and to consider if routine lymph node dissection should be recommended.

The study was undertaken at three departments of surgery and included 14 patients undergoing lung metastasectomy between July 2008 and December 2011. In all patients systematic lymph node dissection was also performed. When wedge resection was done, N1 nodes were removed only as part of a local procedure at that anatomical site. Patients with mediastinal lymph node involvement detected by pre-operative CT or PET scans were not included in the study.

Lung metastasectomy for metastatic sarcoma was performed in 14 patients. Nine patients had bilateral lung metastases. Solitary lung metastasis was found in only one case. The mean number of removed mediastinal lymph nodes was 14.8 (7-32). Mediastinal lymph node metastases were found in two patients (14.3%). The average disease free interval (DFI) was 79.6 months (median, 25.5 months). Using the Kaplan-Meier method, the 3-year survival rate was 46% (0.46±0.15). The Cox-Mantel test for comparing the survival curves showed, at a 0.05 level of significance, better survival rates for the patients with no metastatic lymph node involvement (p=0.01).

The frequency of mediastinal lymph node involvement in our study was 14.3% and this was in agreement with the data reported in the literature. The 3-year survival rate was 46% in our patients; the published 5-year survival is 15-50%. A systematic mediastinal lymphadenectomy during lung metastasectomy for metastatic sarcoma has been recommended, but also argued against because of a low incidence of mediastinal lymph node involvement in sarcomatous metastases reported by some authors. We showed that mediastinal lymph node involvement was a negative prognostic factor. Systematic mediastinal lymphadenectomy as a routine procedure provides for a better staging. This is important in association with the development of adjuvant modalities, such as monoclonal antibodies, at present or a gene therapy in the future.

Even in a carefully selected group of patients, incidence of mediastinal lymph node metastases is high. Since no relevant data based on large patient groups are available, we recommend routine nodal dissection for all patients indicated for lung metastasectomy. Drawing a definite conclusion will require analyses of large numbers of data from multi-institutional studies and cooperation with the international database, if possible.