Development of indication criteria for preoperative examination in lung cancer.

Background Systemic examination for distant metastases is generally recommended for all lung cancer patients. However, this approach rarely detects distant metastases in typically resectable cT1-2N0 non-small-cell lung cancer. The aim of this study was to identify factors associated with distant metastases and develop indication criteria for preoperative systemic examination in patients with cT1-2N0 non-small-cell lung cancer, with a particular focus on computed tomography imaging of primary lesions. Methods We retrospectively reviewed non-small-cell lung cancer patients treated at our institute between 2005 and 2013. Data were extracted and compared between two groups: patients diagnosed as cT1-2N0M0 who underwent complete resection (M0 group, n = 1530) and those diagnosed as cT1-2N0M1b who received systemic chemotherapy (M1 group, n = 26). Results The median age at diagnosis was significantly lower in the M1 group ( p = 0.015). Although carcinoembryonic antigen levels were significantly higher in the M1 group ( p < 0.001), 42% had normal levels. Tumor diameters in lung and mediastinal windows on chest computed tomography were significantly larger, and the proportion (mediastinal/lung window tumor diameter ratio) was higher in the M1 group ( p < 0.001). All 26 patients in the M1 group had a tumor diameter >15 mm and mediastinal/lung window ratio >0.75. Conclusions Preoperative systemic examination is not necessary in cT1-2N0 non-small-cell lung cancer patients when tumor diameters are ≤15 mm and mediastinal/lung window ratios are ≤0.75. According to these criteria, systemic examinations would have been reduced by 40% in our cohort.