T-stage of non-small cell lung cancer directly invading an adjacent lobe

Non-small cell lung cancer (NSCLC) invading the visceral pleura is classified as T2 stage, and NSCLC invading the chest wall, diaphragm, phrenic nerve, mediastinal pleura or parietal pleura is classified as T3. But, there is no definition as to whether tumours directly invading an adjacent lobe beyond the fissure should be classified as T2 or T3. We assessed whether these tumours should be classified as T2 or T3. We evaluated patients with NSCLC who, between 1992 and 2009, underwent complete resection and were pathologically diagnosed as T2 or T3 according to the 7th edition of the TNM classification. To evaluate the effect of the T-stage only, the patients with nodal- and distant metastasis were excluded. Among 837 patients, 499 (59.6%) were pathologically staged as T2a, 91 (10.9%) as T2b and 201 as T3 (24.0%). Forty-six (5.5%) patients had NSCLC with a direct invasion of the adjacent lobe. The mean age (P = 0.102) and sex distribution (P = 0.084) were not statistically significant, but there were more adenocarcinomas in the T2 group than that in the T3 group. The overall survival of the patients with adjacent lobe invasion was statistically worse than that of T2 patients (P = 0.042), but was not statistically different from that of T3 (P = 0.368) patients. There was no difference between the disease-free survival of patients with adjacent lobe invasion and T3 patients (P = 0.306), but disease-free survival of the patients with adjacent lobe invasion was worse than that of T2 (P = 0.003) patients. Considering that the overall survival and disease-free survival of patients with direct adjacent lobe invasion are similar to those of T3, NSCLC with direct invasion to the adjacent lobe should be classified as T3 rather than T2.