RT Journal Article SR Electronic T1 Repeatability of 18F-FDG PET/CT in Advanced Non–Small Cell Lung Cancer: Prospective Assessment in 2 Multicenter Trials JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1137 OP 1143 DO 10.2967/jnumed.114.147728 VO 56 IS 8 A1 Wolfgang A. Weber A1 Constantine A. Gatsonis A1 P. David Mozley A1 Lucy G. Hanna A1 Anthony F. Shields A1 Denise R. Aberle A1 Ramaswamy Govindan A1 Drew A. Torigian A1 Joel S. Karp A1 Jian Q. (Michael) Yu A1 Rathan M. Subramaniam A1 Robert A. Halvorsen A1 Barry A. Siegel YR 2015 UL http://jnm.snmjournals.org/content/56/8/1137.abstract AB PET/CT with the glucose analog 18F-FDG has several potential applications for monitoring tumor response to therapy in patients with non–small cell lung cancer (NSCLC). A prerequisite for many of these applications is detailed knowledge of the repeatability of quantitative parameters derived from 18F-FDG PET/CT studies. Methods: The repeatability of the 18F-FDG signal was evaluated in 2 prospective multicenter trials. Patients with advanced NSCLC (tumor stage III–IV) underwent two 18F-FDG PET/CT studies while not receiving therapy. Tumor 18F-FDG uptake was quantified by measurement of the maximum standardized uptake value within a lesion (SUVmax) and the average SUV within a small volume of interest around the site of maximum uptake (SUVpeak). Analysis was performed for the lesion in the chest with the highest 18F-FDG uptake and a size of at least 2 cm (target lesion) as well as for up to 6 additional lesions per patient. Repeatability was assessed by Bland–Altman plots and calculation of 95% repeatability coefficients (RCs) of the log-transformed SUV differences. Results: Test–retest repeatability was assessed in 74 patients (34 from the ACRIN 6678 trial and 40 from the Merck MK-0646-008 trial). SUVpeak was 11.57 ± 7.89 g/mL for the ACRIN trial and 6.89 ± 3.02 for the Merck trial. The lower and upper RCs were −28% (95% confidence interval [CI], −35% to −23%) and +39% (95% CI, 31% to 54%) in the ACRIN trial, indicating that a decrease of SUVpeak by more than 28% or an increase by more than 39% has a probability of less than 2.5%. The corresponding RCs from the Merck trial were −35% (95% CI, −42% to −29%) and +53% (95% CI, 41% to 72%). Repeatability was similar for SUVmax of the target lesion, averaged SUVmax, and averaged SUVpeak of up to 6 lesions per patient. Conclusion: The variability of repeated measurements of tumor 18F-FDG uptake in patients with NSCLC is somewhat larger than previously reported in smaller single-center studies but comparable to that of gastrointestinal malignancies in a previous multicenter trial. The variability of measurements supports the definitions of tumor response according to PET Response Criteria in Solid Tumors.