Association between vascular FDG uptake during follow-up and the development of thoracic aortic aneurysms in giant cell arteritis

Background

A positive PET scan at diagnosis was associated with a greater yearly increase in ascending and descending aortic diameter and thoracic aortic volume in patients with giant cell arteritis (GCA). Radiologic and histopathologic vascular abnormalities persist in a subset of treated patients despite clinical remission. The aim of this study was to evaluate the association between vascular FDG uptake during follow-up and the development of thoracic aortic aneurysms.

Methods

We recently performed a prospective cohort study of 106 GCA patients, who underwent FDG PET and CT imaging at diagnosis and CT imaging yearly for a maximum of 10 years. In this post hoc analysis, GCA patients who also have had FDG PET imaging during follow-up were included. PET scans were visually scored (0-3) at 7 vascular areas. PET scans were considered positive in case of FDG uptake ≥grade 2 in any large vessel.

Results

Eighty-eight repeat PET scans were performed in 52 out of 106 GCA patients, who were included in the original prospective cohort. Fifty-five (63%) PET scans were done at the time of a relapse and 33 (38%) were done while in remission. Nine out of ten patients with an incident thoracic aortic aneurysm had both a positive PET scan at diagnosis and during follow-up.

Conclusion

In addition to the intensity and extent of the initial vascular inflammation, ongoing aortic inflammation may contribute to the development of thoracic aortic aneurysms in GCA. However, this hypothesis should be confirmed in a large prospective trial with repeat PET scans at predefined time points during follow-up.

Association Between Vascular 18F-Fluorodeoxyglucose Uptake at Diagnosis and Change in Aortic Dimensions in Giant Cell Arteritis : A Cohort Study

BACKGROUND

Previous studies have shown that patients with giant cell arteritis (GCA) who have vascular 18F-fluorodeoxyglucose (FDG) uptake at diagnosis are at increased risk for thoracic aortic complications.

OBJECTIVE

To measure the association between vascular FDG uptake at diagnosis and the change in aortic dimensions.

DESIGN

Prospective cohort study.

SETTING

University Hospitals Leuven.

PATIENTS

106 patients with GCA and FDG positron emission tomography (PET) imaging 3 days or less after initiation of glucocorticoids.

MEASUREMENTS

Patients had PET and computed tomography (CT) imaging at diagnosis and CT imaging yearly for a maximum of 10 years. The PET scans were scored 0 to 3 in 7 vascular areas and summed to a total vascular score (TVS). The PET scan results were positive when FDG uptake was grade 2 or greater in any large vessel. The association between vascular FDG uptake and aortic dimensions was estimated by linear mixed-effects models with random intercept and slope.

RESULTS

When compared with patients with a negative PET scan result, those with a positive scan result had a greater increase in the diameter of the ascending aorta (difference in 5-year progression, 1.58 mm [95% CI, 0.41 to 2.74 mm]), the diameter of the descending aorta (1.32 mm [CI, 0.38 to 2.26 mm]), and the volume of the thoracic aorta (20.5 cm³ [CI, 4.5 to 36.5 cm³]). These thoracic aortic dimensions were also positively associated with TVS. Patients with a positive PET scan result had a higher risk for thoracic aortic aneurysms (adjusted hazard ratio, 10.21 [CI, 1.25 to 83.3]).

LIMITATION

The lengthy inclusion and follow-up period resulted in missing data and the use of different PET machines.

CONCLUSION

Higher TVS was associated with greater yearly increase in thoracic aortic dimensions. Performing PET imaging at diagnosis may help to estimate the risk for aortic aneurysm formation.

PRIMARY FUNDING SOURCE

None.

Prospective comparison of [18F]AlF-NOTA-octreotide PET/MRI to [68Ga]Ga-DOTATATE PET/CT in neuroendocrine tumor patients

BACKGROUND

Fluorine-18-labeled SSAs have the potential to become the next-generation tracer in SSTR-imaging in neuroendocrine tumor (NET) patients given their logistical advantages over the current gold standard gallium-68-labeled SSAs. In particular, [18F]AlF-OC has already shown excellent clinical performance. We demonstrated in our previous report from our prospective multicenter trial that [18F]AlF-OC PET/CT outperforms [68Ga]Ga-DOTA-SSA, but histological confirmation was lacking due to ethical and practical reasons. In this second arm, we therefore aimed to provide evidence that the vast majority of [18F]AlF-OC PET lesions are in fact true NET lesions by analyzing their MR characteristics on simultaneously acquired MRI. We had a special interest in lesions solely detected by [18F]AlF-OC ("incremental lesions").

METHODS

Ten patients with a histologically confirmed neuroendocrine tumor (NET) and a standard-of-care [68Ga]Ga-DOTATATE PET/CT, performed within 3 months, were prospectively included. Patients underwent a whole-body PET/MRI (TOF, 3 T, GE Signa), 2 hours after IV injection of 4 MBq/kg [18F]AlF-OC. Positive PET lesions were evaluated for a corresponding lesion on MRI. The diagnostic performance of both PET tracers was evaluated by determining the detection ratio (DR) for each scan and the differential detection ratio (DDR) per patient.

RESULTS

In total, 195 unique lesions were detected: 167 with [68Ga]Ga-DOTATATE and 193 with [18F]AlF-OC. The DR for [18F]AlF-OC was 99.1% versus 91.4% for [68Ga]Ga-DOTATATE, significant for non-inferiority testing (p = 0.0001). Out of these 193 [18F]AlF-OC lesions, 96.2% were confirmed by MRI to be NET lesions. Thirty-three incremental lesions were identified by [18F]AlF-OC, of which 91% were confirmed by MRI and considered true positives.

CONCLUSION

The DR of [18F]AlF-OC was numerically higher and non-inferior to the DR of [68Ga]Ga-DOTATATE. [18F]AlF-OC lesions and especially incremental lesions were confirmed as true positives by MRI in more than 90% of lesions. Taken together, these data further validate [18F]AlF-OC as a new alternative for SSTR PET in clinical practice. Trial registration ClinicalTrials.gov: NCT04552847. Registered 17 September 2020, https://beta.

CLINICALTRIALS

gov/study/NCT04552847.

Higher diagnostic yield of 18F-FDG PET in inflammation of unknown origin compared to fever of unknown origin

OBJECTIVE

18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) is an important imaging technique in the workup of fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Studies comparing the diagnostic yield of 18F-FDG PET between both entities are lacking.

METHODS

Retrospective analysis of FUO/IUO patients who underwent 18F-FDG PET between 2000 and 2019 in the University Hospitals of Leuven (Belgium). 18F-FDG PET images were assessed for accuracy and contribution towards the final diagnosis. Logistic regression was performed to evaluate the association between meeting FUO or IUO criteria and diagnostic contribution of 18F-FDG PET with and without adjustment for confounders.

RESULTS

Out of 604 patients, 439 (73%, mean age 56 years, 43% female) underwent 18F-FDG PET imaging, including 349 (79%) classified as FUO and 90 (21%) as IUO. Noninfectious inflammatory disorders were significantly more frequent in the IUO group (37% versus 25%; P = 0.03). 18F-FDG PET imaging had a sensitivity of 93% (89-96%), a specificity of 35% (29-42%), and made a positive contribution to the final diagnosis in 25% (21-29%) of cases. IUO was significantly associated with contributive 18F-FDG PET imaging compared to FUO (aOR 2.21 [95% CI 1.31-3.72]; P = 0.003). Among those with contributive 18F-FDG PET imaging, giant cell arteritis (IUO 25% versus FUO 12%) and polymyalgia rheumatica (IUO 17% versus FUO 1%) were numerically more frequent in the IUO group.

CONCLUSION

The diagnostic contribution of 18F-FDG PET was higher among those with IUO, most likely due to differences in diagnostic spectrum.

18F-AlF-NOTA-octreotide outperforms 68Ga-DOTA-TATE/-NOC PET in neuroendocrine tumor patients: results from a prospective, multicenter study

Fluorine-18-labeled somatostatin analogs (SSAs) could represent a valid alternative to the current gold standard gallium-68-labeled SSAs for somatostatin receptor (SSTR) imaging in patients with neuroendocrine tumors (NETs), given their logistical advantages. Recently, ¹⁸F-AlF-NOTA-octreotide (¹⁸F-AlF-OC) has emerged as a promising candidate, but a thorough comparison with ⁶⁸Ga-DOTA-SSA in large patient groups is needed. This prospective, multicenter trial aims to demonstrate non-inferiority of ¹⁸F-AlF-OC compared with ⁶⁸Ga-DOTA-SSA PET in NET patients (ClinicalTrials.gov: NCT04552847). Methods: Seventy-five patients with histologically confirmed NET and a routine clinical ⁶⁸Ga-DOTATATE (n = 56) or ⁶⁸Ga-DOTANOC (n = 19) PET, performed within a 3-month interval of the study scan (median: 7 days; range: -30 to +32 days), were included. Patients underwent a whole-body PET, two hours after IV injection of 4 MBq/kg ¹⁸F-AlF-OC. A randomized, blinded consensus read was performed by two experienced readers to count tumor lesions. Following unblinding, the detection ratio (DR) was determined for each scan, i.e. the fraction of lesions detected on a scan compared to the union of lesions of both scans. The differential detection ratio (DDR; difference in DR between ¹⁸F-AlF-OC and ⁶⁸Ga-DOTATATE/NOC) per patient was calculated. Tracer uptake was evaluated by comparing SUV_max and tumor-to-background ratios (TBRs) in concordant lesions. Results: In total, 4709 different tumor lesions were detected, 3454 with ⁶⁸Ga-DOTATATE/NOC and 4278 with ¹⁸F-AlF-OC. The mean DR with ¹⁸F-AlF-OC was significantly higher than with ⁶⁸Ga-DOTATATE/NOC (91.1% vs. 75.3%; P<10-5). The resulting mean DDR was 15.8% with a lower margin of the 95% confidence interval (95% CI: 9.6%-22.0%) higher than -15%, the pre-specified boundary for non-inferiority. The mean DDR for the ⁶⁸Ga-DOTATATE and ⁶⁸Ga-DOTANOC subgroups were 11.8% (95% CI: 4.3-19.3) and 27.5% (95% CI: 17.8-37.1), respectively. The mean DDR for most organs was higher than zero, except for bone lesions (mean DDR -2.8% (95% CI: -17.8-12.2)). No significant differences in mean SUV_max were observed (P = 0.067), but mean TBR was significantly higher with ¹⁸F-AlF-OC than with ⁶⁸Ga-DOTATATE/NOC (31.7±36.5 vs. 25.1±32.7; P = 0.001). Conclusion: ¹⁸F-AlF-OC is non-inferior and even superior compared with ⁶⁸Ga-DOTATATE/NOC PET in NET patients. This validates ¹⁸F-AlF-OC as an option for clinical practice SSTR PET.

Diagnostic accuracy and validation of 18F-fluorodeoxyglucose positron emission tomography scores in a large cohort of patients with polymyalgia rheumatica

Background

Several studies have shown that ¹⁸F-FDG PET may contribute to the diagnosis of polymyalgia rheumatica (PMR). Previously, we developed a composite PET score called the Leuven score, which was recently adapted to the more concise Leuven/Groningen score by van der Geest et al. The aim of this study is to validate and compare the diagnostic accuracy and cut-off points of both scores in a large cohort of PMR patients.

Methods

Patients with a possible clinical diagnosis of PMR and a PET scan prior to the initiation of glucocorticoids between 2003 and 2020 were included retrospectively. The gold standard for the diagnosis of PMR was the judgment of two experienced clinicians after a follow-up of at least 6 months. FDG uptake was scored visually in 12 articular regions (scores 0–2) and a total skeletal score was calculated by summing the individual scores (maximum of 24 for the Leuven score and 14 for the Leuven/Groningen score). Receiver operating characteristic (ROC) analysis and the Youden index were used to determine the diagnostic accuracy and optimal cut-off points.

Results

A total of 162 patients with PMR and 83 control patients were included. Both PET scores showed high diagnostic accuracy in the ROC analysis (area under the curve 0.986 and 0.980, respectively). The Leuven Score provided a sensitivity of 91.4%, specificity of 97.6% and accuracy of 93.5% at its predefined cut-off point of 16. With the newly determined cut-off point of 12 the sensitivity was 98.8%, the specificity 95.2% and the accuracy 97.6%. The Leuven/Groningen score had a sensitivity, specificity and accuracy of 93.2%, 95.2%, and 93.9%, respectively, with the pre-specified cut-off point of 8, and 96.9%, 92.8%, and 95.5% with the optimal cut-off point of 7.

Conclusion

The original Leuven score and the simplified Leuven/Groningen score both had excellent diagnostic accuracy. The latter may be easier to apply in clinical practice.