Somatostatin receptor positron emission tomography/computed tomography imaging in Merkel cell carcinoma.

BACKGROUND: Merkel cell carcinoma (MCC) is an uncommon aggressive primary cutaneous carcinoma with neuroendocrine differentiation. However, literature data about the use of somatostatin receptor positron emission tomography/computed tomography (PET/CT) imaging in MCC are limited and its role is not clearly stated. OBJECTIVE: To investigate the role of PET/CT using somatostatin analogues radiolabelled with gallium-68 in patients with MCC. METHODS: All patients affected by MCC who performed a somatostatin receptor PET/CT imaging from October 2007 to May 2014 were retrospectively analysed. The diagnostic performances of PET/CT were evaluated on a patient-based analysis and compared to final diagnosis (histology = 3 or clinical/radiological follow-up = 20). RESULTS: We evaluated 23 consecutive MCC patients [18 men; median age 71 years (range 47-87)]. Primary tumour was located in ear (1/23), cheek (3/23), arm (2/23), hand (1/23), back (1/23), anal canal (1/23), gluteus (4/23), thigh (3/23) and popliteal fossa (1/23). In 6/23 patients, the site of primary tumour was unknown. PET/CT was performed to detect primary tumour site (4/23) or to stage (8/23) or re-stage (11/23) patients. PET/CT resulted positive in 14/23 patients and according to the final diagnosis was defined true positive, true negative, false positive (FP) and false negative in 11/23, 8/23, 3/23 and 1/23 cases respectively. FP PET/CT results were due to unspecific liver uptake, post-surgical inflammation and pancreatic neuroendocrine tumour. PET/CT was unable to detect primary tumour site in all patients with unknown primary MCC. Sensitivity, specificity and diagnostic accuracy of PET/CT were 92%, 73% and 83% respectively. CONCLUSIONS: In our experience, somatostatin receptor PET/CT imaging resulted useful in patients with MCC and presented high diagnostic performances with a significant impact in disease management although in patients with unknown primary MCC, it was unable to identify the primary tumour site.

Does a 6-point scale approach to post-treatment 18F-FDG PET-CT allow to improve response assessment in head and neck squamous cell carcinoma? A multicenter study.

PURPOSE: Response assessment to definitive non-surgical treatment for head and neck squamous cell carcinoma (HNSCC) is centered on the role of 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET-CT) 12 weeks after treatment. The 5-point Hopkins score is the only qualitative system available for standardized reporting, albeit limited by suboptimal positive predictive value (PPV). The aim of our study was to explore the feasibility and assess the diagnostic accuracy of an experimental 6-point scale ("Cuneo score"). METHODS: We performed a retrospective, multicenter study on HNSCC patients who received a curatively-intended, radiation-based treatment. A centralized, independent qualitative evaluation of post-treatment FDG-PET/CT scans was undertaken by 3 experienced nuclear medicine physicians who were blinded to patients' information, clinical data, and all other imaging examinations. Response to treatment was evaluated according to Hopkins, Cuneo, and Deauville criteria. The primary endpoint of the study was to evaluate the PPV of Cuneo score in assessing locoregional control (LRC). We also correlated semi-quantitative metabolic factors as included in PERCIST and EORTC criteria with disease outcome. RESULTS: Out of a total sample of 350 patients from 11 centers, 119 subjects (oropharynx, 57.1%; HPV negative, 73.1%) had baseline and post-treatment FDG-PET/CT scans fully compliant with EANM 1.0 guidelines and were therefore included in our analysis. At a median follow-up of 42 months (range 5-98), the median locoregional control was 35 months (95% CI, 32-43), with a 74.5% 3-year rate. Cuneo score had the highest diagnostic accuracy (76.5%), with a positive predictive value for primary tumor (Tref), nodal disease (Nref), and composite TNref of 42.9%, 100%, and 50%, respectively. A Cuneo score of 5-6 (indicative of residual disease) was associated with poor overall survival at multivariate analysis (HR 6.0; 95% CI, 1.88-19.18; p = 0.002). In addition, nodal progressive disease according to PERCIST criteria was associated with worse LRC (OR for LR failure, 5.65; 95% CI, 1.26-25.46; p = 0.024) and overall survival (OR for death, 4.81; 1.07-21.53; p = 0.04). CONCLUSIONS: In the frame of a strictly blinded methodology for response assessment, the feasibility of Cuneo score was preliminarily validated. Prospective investigations are warranted to further evaluate its reproducibility and diagnostic accuracy.

[18FDG-PET and large vessel vasculitis: preliminary data on 25 patients]. / 18FDG-PET e vasculiti dei grandi vasi: studio preliminare su 25 pazienti.

OBJECTIVE: To evaluate the predictive value of clinical and biochemical features when compared to 18FDG-PET in the diagnostic work-up of large vessel vasculitis (LVV). METHODS: Twenty-five patients underwent 18FDG-PET for the clinical suspect of LVV. All of them presented history of systemic symptoms lasting >or=6 months and laboratoristic evidence of persistently high markers of inflammation. The patients were stratified according with: i) clinical manifestations, defined as presence of one or more ACR criteria for the classification of LVV; ii) laboratory investigations: Erythrocyte Sedimentation Rate (ESR) higher or lower than 50 mm/h, C-Reactive Protein (CRP) higher or lower than 2 mg/dl; iii) prednisone dose in the 4 weeks preceding PET examination. RESULTS: The total number of positive PET was higher in the group without clinical ACR criteria and in the group with inflammation markers under the established cut-off. The number of scans consistent with LVV was higher in the groups presenting one or more clinical criteria for LVV but in those with very high ESR and CRP. In all the cases differences between groups were not statistically significative. A clear cut negative correlation between steroid dose and number of scans suggestive for LVV has been observed. CONCLUSIONS: Diagnosis of LVV remains challenging, especially in patients presenting with a constellation of non-specific symptoms and laboratory findings. In this study, both clinical and biochemical features show low correlation with a vasculitic pattern of FDG uptake. In our experience 18FDG-PET represents an useful diagnostic tool in early stages of LVV and a powerful instrument to follow the treatment responses.