Occult Nodal Metastasis Defined by PET-CT Identifies a Unique Clinical Subtype of Lung Cancer: A Retrospective Multicenter Study

Purpose: To investigate the surgical prognosis and efficacy of adjuvant therapy in non-small cell lung cancer (NSCLC) with occult lymph node metastasis (ONM) defined by positron emission tomography-computed tomography (PET-CT).MethodsA total of 3537 NSCLC patients receiving surgical resection were included in this study. The prognosis between patients with ONM and evident nodal metastasis, ONM patients with and without adjuvant therapy were compared, respectively.ResultsONM was associated with significantly better prognosis than evident nodal metastasis whether for patients with N1 (5-year OS: 56.8% versus 52.3%, adjusted p value=0.267; 5-year RFS: 44.7% versus 33.2%, adjusted p value=0.031) or N2 metastasis (5-year OS: 42.8% versus 32.3%, adjusted p value=0.010; 5-year RFS: 31.3% versus 21.6%, adjusted p value=0.025). In ONM population, patients receiving adjuvant therapy yielded better prognosis comparing to those without adjuvant therapy (5-year OS: 50.1% versus 33.5%, adjusted p value<0.001; 5-year RFS: 38.4% versus 22.1%, adjusted p value<0.001). ConclusionsONM defined by PET-CT identifies a unique clinical subtype of lung cancer, ONM is a favorable prognostic factor whether for pathological N1 or N2 NSCLC and adjuvant therapy could provide additional survival benefits for ONM patients.