Repeatability of 18F-FDG PET in a multicenter phase I study of patients with advanced gastrointestinal malignancies

Abstract

18F-FDG PET is often used to monitor tumor response in multicenter oncology clinical trials. This study assessed the repeatability of several semiquantitative standardized uptake values (mean SUV [SUV mean], maximum SUV [SUVmax], peak SUV [SUV peak], and the 3-dimensional isocontour at 70% of the maximum pixel value [SUV70%]) as measured by repeated baseline 18F-FDG PET studies in a multicenter phase I oncology trial. Methods: Double-baseline 18F-FDG PET studies were acquired for 62 sequentially enrolled patients. Tumor metabolic activity was assessed by SUVmean, SUV max, SUVpeak, and SUV70%. The effect on SUV repeatability of compliance with recommended image-acquisition guidelines and quality assurance (QA) standards was assessed. Summary statistics for absolute differences relative to the average of baseline values and repeatability analysis were performed for all patients and for a subgroup that passedQA, in both amulti- and a single-observer setting. Intrasubject precision of baseline measurements was assessed by repeatability coefficients, intrasubject coefficients of variation (CV), and confidence intervals onmean baseline differences for all SUV parameters. Results: The mean differences between the 2 SUV baseline measurements were small, varying from22.1%to 1.9%, and the 95% confidence intervals for these mean differences had a maximum half-width of about 5.6% across the SUV parameters assessed. For SUVmax, the intrasubject CV varied from 10.7% to 12.8% for the QA multi- and single-observer datasets and was 16% for the full dataset. The 95% repeatability coefficients ranged from 228.4% to 39.6% for the QA datasets and up to 234.3% to 52.3% for the full dataset. Conclusion: Repeatability results of double-baseline 18F-FDG PET scans were similar for all SUV parameters assessed, for both the full and the QA datasets, in both the multi- and the single-observer settings. Centralized quality assurance and analysis of data improved intrasubject CV from 15.9% to 10.7% for averaged SUVmax. Thresholds for metabolic response in the multicenter multiobserver non-QA settings were 234% and 52% and in the range of 226% to 39% with centralized QA. These results support the use of 18F-FDG PET for tumor assessment in multicenter oncology clinical trials. Copyright © 2009 by the Society of Nuclear Medicine, Inc.