The prognostic impact of the mediastinal fat tissue invasion in patients with non-small cell lung cancer.

BACKGROUND The prognosis of the mediastinal fat tissue invasion in non-small cell lung cancer (NSCLC) patients has not yet been clearly defined. The present study aimed to investigate the prognostic impact of the mediastinal fat tissue invasion in NSCLC patients. METHOD We analyzed 36 patients who were found mediastinal fat tissue invasion by pathological evaluation (mediastinal fat group) and 248 patients who were classified as T4-NSCLC according to the 8th TNM classification (T4 group; invasion of other mediastinal structures in 78 patients, ipsilateral different lobe satellite pulmonary nodule in 32 patients, and tumor diameter > 7 cm in 138 patients). RESULT Resection was regarded as complete (R0) in 255 patients (89.7%). Mediastinal fat group showed significantly higher incidence of incomplete resection (R1) and more left-sided tumors than the T4 group (p = 0.01, and p = 0.002, respectively). The survival was better in T4 group than mediastinal fat group (median 57 months versus 31 months), although it was not significant (p = 0.205). Even when only N0/1 or R0 patients were analyzed, the survival was not different between two groups (p = 0.420, and p = 0.418, respectively). 5-year survival rates for T4 subcategories (invasion of other structures, ipsilateral different lobe pulmonary nodule, and tumor diameter > 7 cm) were 39.4%, 41.9%, and 50.3%, respectively (p = 0.109). Multivariate analysis showed that age (p < 0.0001), nodal status (p = 0.0003), and complete resection (p < 0.0001) were independently influenced survival. CONCLUSION There is no significant difference in the prognosis between mediastinal fat tissue invasion and T4 disease in NSCLC patients.