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

ObjectiveNon–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.MethodsWe 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.ResultsThe 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.ConclusionsStage 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.