Risk Factors for Predicting Occult Lymph Node Metastasis in Patients with Clinical Stage I Non-small Cell Lung Cancer Staged by Integrated Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

Background Lymph nodes in patients with non-small cell lung cancer (NSCLC) are often staged using integrated 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT). However, this modality has limited ability to detect micrometastases. We aimed to define risk factors for occult lymph node metastasis in patients with clinical stage I NSCLC diagnosed by preoperative integrated FDG-PET/CT. Methods We retrospectively reviewed the records of 246 patients diagnosed with clinical stage I NSCLC based on integrated FDG-PET/CT between April 2007 and May 2015. All patients were treated by complete surgical resection. The prevalence of occult lymph node metastasis in patients with clinical stage I NSCLC was analysed according to clinicopathological factors. Risk factors for occult lymph node metastasis were defined using univariate and multivariate analyses. Results Occult lymph node metastasis was detected in 31 patients (12.6 %). Univariate analysis revealed CEA ( P = 0.04), SUV max of the primary tumour ( P = 0.031), adenocarcinoma ( P = 0.023), tumour size ( P = 0.002) and pleural invasion ( P = 0.046) as significant predictors of occult lymph node metastasis. Multivariate analysis selected SUV max of the primary tumour ( P = 0.049), adenocarcinoma ( P = 0.003) and tumour size ( P = 0.019) as independent predictors of occult lymph node metastasis. Conclusions The SUV max of the primary tumour, adenocarcinoma and tumour size were risk factors for occult lymph node metastasis in patients with NSCLC diagnosed as clinical stage I by preoperative integrated FDG-PET/CT. These findings would be helpful in selecting candidates for mediastinoscopy or endobronchial ultrasound-guided transbronchial needle aspiration.