Importance of lymph node dissection in thymic carcinoma.

BACKGROUND: Lymph node dissection plays important role in oncologic surgery. We investigated outcomes of lymph node dissection in thymic carcinoma.

METHODS: We retrospectively reviewed 37 patients, who underwent complete resection for thymic carcinoma. Patients were divided into four groups: no node dissection (Nx), 8; pathologic N0 by limited dissection (N0a), 13; pathologic N0 by extensive dissection (N0b), 10; and node metastasis (N1), 6. Outcomes of lymph node dissection were investigated. Disease-free survival (DFS) and freedom from recurrence of the four groups were compared.

RESULTS: A total of 349 lymph nodes were dissected in 29 patients. Metastasis was confirmed in 19 nodes in 6 patients, with tumor invading adjacent organs. Anterior mediastinal lymph node metastasis was confirmed in 4 patients. Intrathoracic lymph node metastasis was confirmed in 3 patients at the right paratracheal lymph nodes. Recurrences were diagnosed in 11 patients (Nx, 2; N0a, 4; N0b, 1; N1, 4). The 5-year overall survival rate was 65.5%, DFS was 60.9%, and freedom from recurrence was 68.2%. DFS rates of the N0b subgroup were significantly better than in the N1 subgroup (90% vs 33.3%). DFS rates of the Nx and N0a subgroups were similar (75% vs 48.7%, p=0.98), and the prognoses of both groups were intermediate between the N0b and N1 groups. Analyses of freedom from recurrence proved identical results.

CONCLUSIONS: Extensive lymph node dissection, meaning dissection of more than 10 lymph nodes, is required to predict prognosis accurately. Anterior mediastinal and right paratracheal lymph nodes should be dissected in thymic carcinoma.