Risk Factors for Occult Mediastinal Metastases in Clinical Stage I Non-Small Cell Lung Cancer

In patients deemed to have clinical stage I for non-small cell lung cancer (NSCLC) after computerized tomography (CT) and positron emission tomography (PET) scans, the utility of mediastinoscopy to detect occult mediastinal metastases is unclear. The goal of this study was to analyze the risk factors for occult mediastinal metastases in this subset of patients.We conducted a retrospective review during a 7-year period to identify patients with potentially operable clinical stage I NSCLC screened by CT and PET scans. Medical records were reviewed, and the prevalence of pathologic N2 disease was analyzed according to clinical tumor location, size, histology, and PET uptake of the primary tumor.Of 224 patients identified with clinical stage I NSCLC with a CT-negative and PET-negative mediastinum, 16 patients had pathologic N2 disease proven by mediastinoscopy (n = 11) or after resection (n = 5). The overall prevalence of histologically confirmed N2 disease was 6.5% in clinical T1 patients and 8.7% in clinical T2 patients. Central tumors had a higher prevalence of N2 disease compared with peripheral tumors, 21.6% versus 2.9% (p < 0.001). Larger clinical T size predicted a higher prevalence of occult N2 disease (p < 0.001). All 16 patients with occult N2 metastases had adenocarcinoma as the primary tumor cell type. When the PET maximum standardized uptake value (SUV(max)) of the primary tumors was analyzed, patients with occult N2 metastases had a higher median SUV(max) of the primary tumor compared with patients without N2 metastases, 6.0 g/mL versus 3.6 g/mL (p = 0.017).For patients deemed at clinical stage I NSCLC by CT and PET, the prevalence of missed N2 metastases increased significantly with larger tumor size and central location. Adenocarcinoma cell type and a high PET SUV(max) of the primary tumor were other risk factors. Mediastinoscopy may have improved yield in the select subset of patients with one or more risk factor.