Syndromes paranéoplasiques : intérêt de la tomographie par émission de positons (TEP) au 18F-fluoro-déoxyglucose (FDG)

BackgroundWe evaluated the performance of ¹⁸F-fluorodeoxyglucose (¹⁸FDG) positon emission tomography (PET) in the diagnosis of underlying malignancy in cases of suspected paraneoplastic syndrome (PS).Methods¹⁸FDG-PET was performed in 31 patients, clinically suspected to have PS. The PS were 34, among which 12 neurological diseases, eight endocrine, seven rheumatological, one dermatological and six vascular. We compared computed tomography (CT), iodine-enhanced most of the time, and ¹⁸FDG-PET reports to clinicians definitive conclusion at the end of the work-up and a follow-up period of, at least, two months.ResultsWe obtained a histological diagnosis of cancer for ten patients, but could only identify the primary site of malignancy for nine of them. ¹⁸FDG-PET showed six primary sites among which three were not seen on CT. CT disclosed four primary sites, among which one was not seen on ¹⁸FDG-PET. In one case, ¹⁸FDG-PET disclosed regional lymph node metastases whereas these were not identified by CT. Eleven non-neoplasic causes were evidenced, among which ¹⁸FDG-PET played a major role in three cases. Ten causes were still undetermined at the end of the study.ConclusionWhole-body ¹⁸FDG-PET study plays an important role in the identification of underlying malignancy in clinically suspected paraneoplastic syndromes; either by identifying the primary tumor or by directing biopsy of metastases. Furthermore, it can identify non-neoplasic causes.     

Place de la tomographie par émission de positons (TEP) au [18F]FDG dans l’exploration des vascularites

[¹⁸F]fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) is a noninvasive metabolic imaging modality that is well suited to the assessment of activity and extent of large vessel vasculitis, such as giant cell arteritis and Takayasu arteritis. PET could be more effective than magnetic resonance imaging in detecting the earliest stages of vascular wall inflammation. The visual grading of vascular [¹⁸F]FDG uptake makes it possible to discriminate arteritis from atherosclerosis, providing therefore high specificity. High sensitivity can be achieved provided scanning is performed during active inflammatory phase, preferably before starting corticosteroid treatment. Large scale prospective studies are needed to determine the exact value of PET imaging in assessing the large vessel vasculitis outcome and response to immunosuppressive treatment.     

Comparaison de différentes méthodes de segmentation en TEP/TDM pour le ciblage en radiothérapie des carcinomes épidermoïdes des VADS

IntroductionTo assess interobserver variability for biological target volume (BTV) delineation and to compare the reproductibility of different semiautomatic segmentation methods in pretreatment 18-fluorodeoxyglucose positron emission tomography (PET/CT) of head and neck squamous cell carcinoma (HNSCC).Patients and methodsPatients with histologically proved HNSCC referred to the nuclear medicine service in Brest for pretreatment PET/CT were prospectively included from February 2009 to June 2010. Three nuclear medicine physicians (two specialized in oncology) delineated manually and independently BTV on each primary tumor. Four semiautomatic segmentation methods have been studied; three using a fixed threshold and one applying an adaptive threshold based on the signal-to-background ratio (Daisne). The variability between κ observers and/or methods has been assessed. The concordance between the various BTV intersections and unions has been also assessed.ResultsThirty patients (29M; 1F) were included. The primary site location was oropharynx in six patients, oral cavity in 10 patients, hypopharynx in five patients and larynx in nine patients. A statistically significant global interobserver variability (P = 0.01) was showed, but without statistically difference between the two experienced oncologists (P = 0.15). The maximal concordance of the two experienced observers with the semiautomatic methods was found for the Daisne method (CI = 61.5%; κ = 0.68), expressing a good agreement according to the Landis and Koch criteria, better than with the segmentation method using a fixed threshold with 40% of maximal signal intensity (CI = 52.1%; κ = 0.53).ConclusionOur results suggest the feasibility of achieving HNSCC BTV delineation by PET/CT using semiautomatic methods, in particular those which apply an adaptative threshold but under the supervision of an experienced operator.     

Évaluation des thérapeutiques ciblées en tomographie par émission de positons

Thanks to breakthroughs in drug design, new kinds of treatment in oncology have been developed. These new molecules target usually a precise molecular pathway proved to be involved in the development of a malignant disease. This led to the concept of targeted therapy. Therefore, the accurate selection of patients who may experience a clinical benefit of such treatments and the way to assess the response are still challenging issues. Molecular imaging with radiolabeled compounds seemed to be a very promising tool, as for example PET with ¹⁸F FluoroDeoxyGlucose (FDG), which allows to assess and to predict the response to a tyrosine kinase inhibitors more efficiently than conventional imaging tools. FDG is only a surrogate marker of cell proliferation. The common tools (clinical and radiological assessment) are no longer sufficient to predict the clinical efficacy of these new drugs. Molecular imaging should be added in the design of clinical trials in order to detect earlier pharmacodynamic effects, to select responding patients and to provide proofs of efficacy of these non-cytotoxic compounds. Molecular imaging databases have to be created and cross-matched to tumor sample collections, providing consequently new “dynamic” pathological resources.     

La tomographie par émission de positons (TEP) hors oncologie : l’exploration du cerveau

Positron emission tomography (PET) allows evaluation of the central nervous system function. Imaging of regional cerebral blood flow and metabolism, and of several neurotransmission systems may be obtained using PET. PET quantification is accurate and has good test–retest reliability. For research purposes, PET has been used to study brain physiology, to explore neurological and psychiatric diseases patophysiology and for the new drugs research and development. FDG is the only PET radioligand with clinical application. Following criteria of evidence-based medicine, the clinical indications of FDG-PET are: evaluation of treated gliomas, presurgical study of partial refractory epilepsy and diagnosis of Alzheimer's disease when it is impossible to differentiate clinically from frontotemporal dementia.     

Intérêt complémentaire de la TEP/TDM au FDG et de l’imagerie conventionnelle dans le bilan initial et le suivi post-thérapeutique des cancers des VADS : recommandations et perspectives

Functional imaging by ¹⁸fluorodesoxyglucose (FDG) positron emission tomography (PET) and morphological imaging by computed tomography (CT) and magnetic resonance imaging (MRI) hold an important and complementary role in characterization of head and neck squamous cell carcinoma (HNSCC). Based on an exhaustive literature, the recommendations and perspectives of their use in the initial assessment and the post-therapeutic management of HNSCC are presented.     

Place de la tomographie d’émission de positons (TEP) pour l’évaluation thérapeutique et le suivi du cancer du sein

Positron emission tomography (PET) with fluorodeoxyglucose (FDG) is a nuclear imaging method whose interest in oncology has only grown over the past fifteen years. This article summarizes the results in monitoring and therapeutic evaluation of breast cancer. For the search of locoregional or distant recurrence, the performance of FDG-PET are very interesting. The impact of FDG-PET on the therapeutic management is undeniable. For therapeutic evaluation, this imaging is useful to evaluate the neoadjuvant chemotherapy and hormonotherapy efficacy. FDG-PET is indicated in cases of suspected recurrence (clinical, biological or imaging suspicious). It is the most sensitive exam for the detection of bone or visceral metastases. It allows the re-staging during a relapse proved whether local or remote, and can change the therapeutic management.     

Bilan initial d’imagerie de l’adénocarcinome pancréatique : données de la littérature sur la place actuelle de la tomographie par émission de positons au 18F-fluorodéoxyglucose (TEP FDG)

In pancreatic adenocarcinoma, initial imaging is essential to better select patients for surgery. Recent literature analysis of F18-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET) in pancreatic adenocarcinoma is summarized in the present article. Performances of FDG PET in the fields of lymph node involvement, metastatic involvement and therapeutic efficacy assessment are described for its correct use in pancreatic adenocarcinoma.     

Détection fortuite d’une synovite villonodulaire extra-articulaire du muscle psoas en tomographie par émission de positons au 18F-fluorodésoxyglucose

Pigmented villonodular synovitis (PVNS) is a benign but locally aggressive disorder, which commonly involves large joints. This article reports a rare case of an extra-articular PVNS located within the left psoas muscle. This lesion has been accidentally discovered during a follow-up FDG PET/CT. The patient was asymptomatic and did not undergo any surgery. This article reports that FDG PET/CT could be helpful for monitoring PVNS.     

Apport de la tomographie à émission de positons au 18F-fluorodéoxyglucose dans la prise en charge des lymphomes folliculaires

PurposeTo assess the usefulness of positron emission tomography/computed tomography in staging, prognosis evaluation and restaging of patients with follicular lymphoma.Patients and methodsa retrospective study was performed on 45 patients with untreated biopsy-proven follicular lymphoma who underwent FDG-PET/CT and CT before and after chemo-immunotherapy induction treatment (rituximab combined with cyclophosphamide, doxorubicin, vincristine and prednisone).ResultsPET/CT detected more nodal (+51%) and extranodal (+89%) lesions than CT. PET/CT changed Ann Arbor stage in eight patients (18%). Five patients (11%) initially considered with early stage (I/II) were finally managed as advanced stage (III/IV). In this study, initial PET/CT was significantly more accurate to identify patients with poor prognosis than FLIPI. Poor prognosis was defined as incomplete therapeutic response or early relapse. Accuracy of PET/CT for therapeutic response assessment was significantly higher than that of CT (0.97 vs 0.64), especially because of its ability to identify inactive residual masses. Beside, post-treatment PET/CT was able to predict patients’ outcome. The median progression free survival (PFS) was 48 months in the PET/CT negative group as compared to 17.2 months for the group with residual uptake (P < 10^?4).ConclusionFDG-PET/CT is a very useful tool for staging, assessing prognosis and therapeutic response of patients with follicular lymphoma.