Repeatability of quantitative uptake measures of whole body [F-18]FDG PET/CT in NSCLCpatients

1379 Objectives Change in [18F]FDG uptake might predict response to anticancer treatment. The PET Response Criteria in Solid Tumors (PERCIST) suggest a threshold of 30% change in SUV to define partial response and progressive disease1. Evidence underlying these thresholds consists of mixed data from stand-alone PET and PET/CT scanners with variable uptake intervals2. There is an increasing interest in alternative [18F]FDG uptake measures such as metabolic active tumor volume (MATV) and total lesion glycolysis (TLG). The aim of this study was to investigate the test-retest repeatability (TRT) of various quantitative whole body [18F]FDG metrics in NSCLC patients as a function of tracer uptake interval. Methods Ten NSCLC patients, with at least one intrahoracic lesion ≥ 3cm, underwent double baseline whole body [18F]FDG PET/CT scans at 60 and 90 minutes post injection within 3 days. Scans were obtained following the EANM guideline recommendations. [18F]FDG avid tumors were delineated with a 50% threshold of SUVpeak, corrected for local background. SUVmax/mean/peak, TLG, MATV and tumor-to-blood and liver ratios were determined. Results TRT was better for SUVmax/mean/peak in the 90 vs. 60 min data when all lesions (n=58) were included (Wilcoxon: p 0.97 and R2\u003e0.98 for all uptake measures. Normalisation for liver or blood uptake did not improve TRT. Conclusions Differences in TRT between 60 and 90 minutes data are small, however these differences are no longer significant when only PERCIST target lesions are included. PERCIST applied to scans obtained at 60 min post injection seems therefore a good strategy for evaluation of treatment response.