Intrapulmonary metastasis in resected pathologic stage IIIB non-small cell lung cancer: Possible contribution of aerogenous metastasis to the favorable outcome

Objective: Non-small cell lung cancer with pulmonary metastasis in the primary lobe (PM+) is classified as pathologic stage IIIB. Although stage IIIB PM+ indicates a poor prognosis, this stage includes various subgroups with heterogeneous clinical outcomes. The objective of this study was to extract a subgroup of patients with stage IIIB PM+ non-small cell lung cancer with a better prognosis and assess their biological characteristics and metastatic mechanisms. Methods: We reviewed 122 cases of surgically resected stage IIIB PM+ non-small cell lung cancer and extracted a subgroup with a favorable outcome by univariate analysis of clinicopathologic factors. The 15 cases without lymph node metastasis and vessel invasion (PM+/ N-/VI-) were extracted as the most favorable group. We assessed the clinicopathologic features of the PM+/N-/VI- group in comparison with the other patients with stage IIIB PM+ disease. Results: The disease-specific survival of the PM+/N-/VI- group was significantly better than that of the other stage IIIB PM+ group. Microscopic characteristics of the metastatic lesions suggesting that the cancer cells had invaded via the aerogenous route were seen in 86.7% of the (PM+/N-/ VI-) group, as opposed to only 9.4% of the other PM+ cases. Furthermore, in all 4 patients in the PM+/N-/VI- group who had a recurrence, the relapse involved intrapulmonary metastasis, rather than distant organ metastasis. Conclusions: Stage IIIB PM+ cases via the airway route were enriched in the PM+/N-/VI- group and had an extremely good survival. This group should be recognized as having local disease, and if relapse occurs in the remnant lobe, it may be possible to achieve a cure by local therapy.