Dissociation between 2-[18F]fluoro-2-deoxy-D-glucose positron emission computed tomography, ultrasound and clinical assessments in patients with non-severe rheumatoid arthritis, including remission.

BACKGROUND: Inflammation of patients joints with severe disease activity of rheumatoid arthritis (RA) has already been visualized and quantified by 2-[18F]fluoro-2-deoxy-D-glucose positron emission computed tomography ([18F] FDG PET/CT), but little is known about the metabolic status and its relationship with clinical and ultrasonography (US) metrology in patients with low/moderate activity or in remission. METHODS: Clinical assessments [based on 28-joint disease activity score (DAS28-CRP) and Clinical Disease Activity Index (CDAI)], [18F] FDG PET/CT, US and X-ray were performed on 63 RA patients classified into remission or low/moderate or severe disease activity groups. PET/CT was visually and then semi-quantitatively analysed by determining the standardized uptake value (SUV) of positive joints. RESULTS: Of the 1764 joints, 21.1% were tender only, 13.7% swollen only, 27.6% tender or swollen, 7.3% tender and swollen, 20.5% PET/CT-positive and 8.6% US-positive. PET and US measurements were correlated, albeit with poor concordance. The positive predictive value of PET/CT for clinical evaluation (tender and/or swollen) was low, whereas its negative predictive value was high. Highly significant differences were found with the number of PET/CT-positive joints and with cumulative SUV between "severe" and "non-severe" patients (including those in remission and those with low/moderate activity) and not between those classified as "remission" and "non-remission" or "remission" and "low/moderate activity". Moreover, the correlation between PET/CT measurements and clinical activity was positive only in the CDAI severe disease group. In patients in remission or with low/moderate activity, only 20-30% of joints were PET/CT-negative. In remission, PET/CT and US were positive in different joints, and PET/CT-positive but US-negative joints mainly exhibited RA (38.1%) or normal (49.2%) and not osteoarthritic (12.7%) X-ray patterns. CONCLUSIONS: [18F] FDG PET/CT was effective at distinguishing patients with severely active disease from other patients. In non-severe RA patients, including those in remission, PET/CT results are discordant from US and clinical observations. A longitudinal analysis is needed to explore the clinical relevance of such infra-clinical disease.

18F- FDG PET/CT joint assessment of early therapeutic response in rheumatoid arthritis patients treated with rituximab.

BACKGROUND: 18F-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. RESULTS: High 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. CONCLUSIONS: These 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.

For avid glucose tumors, the SUV peak is the most reliable parameter for [(18)F]FDG-PET/CT quantification, regardless of acquisition time.

BACKGROUND: This study is an assessment of the impact of acquisition times on SUV with [(18)F]FDG-PET/CT on healthy livers (reference organ with stable uptake over time) and on tumors. METHODS: One hundred six [(18)F]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-cm(3) spherical volume), and SUVaverage were measured within a 3-cm-diameter volume of interest (VOI) in the right lobe of the liver. For [(18)F]FDG avid tumors (SUVmax ≥ 5), the SUVmax, SUVpeak, and SUV41% (isocontour threshold method) were computed. RESULTS: For 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. CONCLUSIONS: For [(18)F]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.

[¹8F]FDG positron emission tomography within two weeks of starting erlotinib therapy can predict response in non-small cell lung cancer patients.

PURPOSE: The 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 METHODS: Three [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). RESULTS: By 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. CONCLUSION: Morphologic 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.

Unusual uptake of 18FDG by a hepatic adenoma.

Hepatic adenoma is a rare, benign tumor (with potential for malignant degeneration) and its diagnosis is difficult because its presentation is highly variable in medical imaging, particularly with MRI. In such cases, the use of a hepatic biopsy is usually recommended. (18)FDG-PET/CT provides a very significant predictive value for malignant hepatic lesions. In addition, the occurrence of an (18)FDG-avid benign tumor is a rare event. We hereby present the case of a patient with advanced breast cancer for whom an (18)FDG-PET/CT showed a focal hepatic uptake. A subsequent biopsy provided a diagnosis of a hepatic adenoma.

PET in Brain Tumors.

Evaluating gliomas, either at diagnosis or at recurrence, is among the historical indications of FDG positron emission tomography (PET) imaging. There is a clear relationship between the tumor grade, patient prognosis, and intensity of uptake. Yet the exact role of FDG PET imaging remains debated. PET and methionine labeled with the short-lived C11 also have been proposed, with the significant advantage of high tumor-to-cortex contrast and distinct bological properties that lead to specific indications. Clinical use of this tracer is hampered by the need for an on-site cyclotron, however. In recent years, the increased availability of fluorinated amino-acid analogs, in particular FET, has open the way to renewed scientific interest in the field of neuro-oncological PET and PET/CT. This article discusses FDG and alternative tracers for diagnosing and characterizing primary brain tumors, detecting their recurrences, helping to guide the radiation therapy, and for evaluating the response to treatments.

Applications of PET and PET/CT in the Evaluation of Infection and Inflammation in the Skeletal System.

Unlike anatomic imaging modalities, which mainly detect structural changes, positron emission tomography (PET) is a molecular imaging technique able to detect the disease in an early stage and long before anatomic changes are visible. It is well known that fluorodeoxyglucose (FDG) accumulates at the sites of various inflammatory and infectious processes. FDG-PET or FDG-PET/computed tomography (CT) has been successfully used in the evaluation of various nonosseous soft tissue infections. Its application in the evaluation of osseous infection is also promising. This review discusses the potential roles of PET or PET/CT in the evaluation of infection and inflammation in the skeletal system.