BackgroundThis study is an assessment of the impact of acquisition times on SUV with [18F]FDG-PET/CT on healthy livers (reference organ with stable uptake over time) and on tumors.MethodsOne hundred six [18F]FDG-PET/CT were acquired in list mode over a single-bed position (livers (n = 48) or on tumors (n = 58)). Six independent datasets of different durations were reconstructed (from 1.5 to 10 min). SUVmax (hottest voxel), SUVpeak (maximum average SUV within a 1-cm3 spherical volume), and SUVaverage were measured within a 3-cm-diameter volume of interest (VOI) in the right lobe of the liver. For [18F]FDG avid tumors (SUVmax ≥ 5), the SUVmax, SUVpeak, and SUV41% (isocontour threshold method) were computed.ResultsFor tumors, SUVpeak values did not vary with acquisition time. SUVmax displayed significant differences between 1.5- and 5–10-min reconstruction times. SUV41% was the most time-dependent parameter. For the liver, the SUVaverage was the sole parameter that did not vary over time.ConclusionsFor [18F]FDG avid tumors, with short acquisition times, i.e., with new generations of PET systems, the SUVpeak may be more robust than the SUVmax. The SUVaverage over a 3-cm-diameter VOI in the right lobe of the liver appears to be a good method for a robust and reproducible assessment of the hepatic metabolism.

PurposeThe aim of this prospective study was to evaluate whether [18F]FDG-PET/CT, performed within two weeks of starting erlotinib therapy can predict tumor response defined by RECIST 1.1 criteria after 8 weeks of treatment in patients with inoperable (stage IIIA to IV) non-small cell lung cancer patients.Patients and MethodsThree [18F]FDG-PET/CT scans were acquired in 12 patients before (5±4 days) and after 9±3 days (early PET) and 60±6 days (late PET) of erlotinib therapy. Conventional evaluation, including at least chest CT (baseline versus after 8 weeks of treatment), was performed according to RECIST 1.1 criteria. Change in [18F]FDG uptake was compared with conventional response, progression-free survival (PFS), and overall survival (OS).ResultsBy using ROC analysis, the Area Under the Curve for prediction of metabolic non-progressive disease (mNP) by early PET was 0.86 (95% CI, 0.62 to 1.1; P = 0.04) at a cut-off of 21.6% reduction in maximum Standardized Uptake Value (SUVmax). This correctly classified 11/12 patients (7 with true progressive disease; 4 with true non-progressive disease; 1 with false progressive disease). Non-progressive disease after 8 weeks of treatment according to RECIST 1.1 criteria was significantly more frequent in patients classified mNP (P = 0.01, Fisher's exact test). mNP patients showed prolonged PFS (HR = 0.27; 95% CI, 0.04 to 0.59; P<0.01) and OS (HR = 0.34; 95% CI, 0.06 to 0.84; P = 0.03). Late PET analysis provided concordant results.ConclusionMorphologic response, PFS and OS survival in non-small cell lung cancer patients can be predicted by [18F]FDG-PET/CT scan within 2 weeks after starting erlotinib therapy.

Background18F–FDG PET/CT has been proposed in the evaluation of the disease activity in rheumatoid arthritis (RA). The goals of this study were to evaluate the reproducibility of the technique, to compare metabolic parameters to clinical, biological and ultrasonographic parameters before and after treatment and to evaluate whether the early metabolic response was related to the outcome. 18F- FDG PET/CT of the hands, wrists and knees was obtained in 15 patients with anti-TNFα refractory RA, at baseline and 16 weeks after treatment with rituximab. The number of PET-positive joints (PET+ joints), the cumulative standard uptake value (cSUV) and the composite index (CI) were defined. The composite clinical index DAS28, CRP serum levels and the number of joints positive at ultrasonography (US+ joints) and the cumulative synovial thickness (CST) were also assessed at baseline and week 24.ResultsHigh interobserver agreement was observed, both at baseline and after treatment. The number of PET+ joints was not correlated with the number of joints tender or swollen. The 3 metabolic parameters were strongly correlated with US, CRP and DAS28 at baseline and with US and CRP (CSUV, CI) at week 16, but no longer with the DAS28 index. The metabolic response based on the change in the visual PET/CT joint analysis predicted the outcome with a high negative predictive value of 91%, with a 91% specificity, and an 86% accuracy.ConclusionsThese preliminary data suggest that 18F- FDG PET/CT is a reproducible and accurate tool for evaluating disease activity in refractory rheumatoid arthritis and its non-response to rituximab. The correlation obtained with US joint assessment gives relevance to objective diseased joints through imaging techniques.