Morbelli S, et al. - Here, analysts assess the connections between circulating tumor cells (CTCs) or plasma cell-free DNA (cfDNA) on one side and a comprehensive range of ¹⁸F-FDG PET/CT–derived parameters on the other side in chemotherapy-naive patients with advanced non–small cell lung cancer (NSCLC). The correlation of cfDNA levels with tumor metabolism recommends that cfDNA may better reflect tumor biologic behavior or aggressiveness rather than tumor burden in metastatic NSCLC. This is not noted with metabolic tumor volume at regional or distant levels.