Exploring Spatial Overlap of High-Uptake Regions Derived From Dual Tracer Positron Emission Tomography–Computer Tomography Imaging Using (18)F-Fluorodeoxyglucose and (18)F-Fluorodeoxythymidine in Nonsmall Cell Lung Cancer Patients: A Prospective Pilot Study

Interest is growing in radiotherapy to nonuniformly boost radioresistant regions within nonsmall cell lung cancer (NSCLC) using molecular imaging techniques. The complexity of tumor behavior is beyond the ability of any single radiotracer to reveal. We hold dual tracer positron emission tomography–computer tomography (PET/CT) imaging with fluorodeoxyglucose (FDG) and fluorodeoxythymidine (FLT) for NSCLC patients to offer an integrated overlook of tumor biological behaviors quantitatively and localizationally, which may help biological target volume delineation and subvolume boost. Pathological confirmed that NSCLC patients were eligible. FDG and FLT PET/CT were performed for each patient before anticancer treatment and coregistrated for analysis. Maximum and mean standardized uptake values (SUV(max) and SUV(mean)) were calculated automatically. Metabolic volumes (MVs) were delineated by a fixed 50% of SUV(max) in FDG PET/CT and proliferative volumes (PVs) were delineated by 50% to 90% of SUV(max) with 10% interval in FLT PET/CT. Overlap ratio (OR) were determined as overlapped volume between MV and PV divided PV. Conventional contrast-enhanced CT-based intensity-modulated radiotherapy (IMRT) plans with and without additional PET/CT-guided subtarget boost were made for each of the 5 typical NSCLC patients. Dosimetric parameters derived from dose–volume histogram, tumor control probability (TCP), and normal tissue complication probability (NTCP) of lung, esophagus, heart, and spinal cord were calculated and compared. Thirty-one patients were prospectively included and 23 were selected for analysis. Totally, 23 primary diseases, 41 metastatic lymph nodes, and 15 metastatic lesions were positive in dual PET/CTs and included for analysis. Median ORs increased from 58.61% to 93.12% under thresholds of 50% of SUV(max) in FDG PET/CT and increased thresholds from 50% to 90% of SUV(max) in FLT PET/CT. Based on conventional IMRT, additional boost to union of high FDG (determined by 50% SUV(max)) and FLT (determined by 80% SUV(max)) uptake subtargets exhibited higher TCP without significant elevated NTCP of lung, esophagus, spinal cord, and heart. Dual tracer PET/CT of FDG and FLT is suggested for NSCLC patients to guide tumor target delineation in clinical practice. FDG PET/CT is necessary whereas FLT PET/CT may be optional when guiding tumor target delineation clinically. Additional information from randomized trials is required to validate.