Diagnostic performances of [18F]fluorocholine positron emission tomography in brain tumors

BACKGROUND

Brain tumors characterization by molecular imaging that allows the depiction of brain lesions metabolic pattern is crucial. Our study aimed to: 1) to evaluate the diagnostic performances of [18F]fluoroethylcholine positron emission tomography/computed tomography ([18F]FECH PET/CT), and 2) correlate PET imaging derived parameters of [18F]FECH to survival in brain tumors.

METHODS

From 2009 to 2012, we enrolled 30 patients who underwent [18F]FECH PET/CT. Final diagnosis was established by clinical and radiological follow-up.

RESULTS

Final diagnosis was consistent with tumor disease in 27/30 cases. In 3/30 cases tumor disease was ruled out. [18F]FECH PET/CT resulted true positive and negative in 21/30 and 9/30 patients, respectively. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of [18F]FECH PET/CT were 78%, 100%, 100%, 33%, and 80%, respectively. Mean and maximum standardized uptake value (SUVmean and SUVmax) resulted statistically correlated to histology (P=0.0255 and P=0.0222, respectively). Using a SUVmax cut-off of 2.0 or 3.2, we distinguished between low- and high-grade gliomas with a good specificity (70% and 80%, respectively). SUVmax and histology resulted correlated to overall survival and disease related survival at multivariate analysis.

CONCLUSIONS

Our results, worthy of further investigations, show high diagnostic performances of [18F]FECH PET/CT, and a correlation between PET imaging derived parameters and survival.

The role of imaging in the diagnosis of recurrence of primary seminal vesicle adenocarcinoma

Primary seminal vesicle (SV) adenocarcinoma is a rare tumor. A small amount of data about the role of imaging to detect tumor recurrence is available. We report the case of a 58-year-old patient with primary SV clear-cell well-differentiated adenocarcinoma. Clinical and instrumental examinations were negative for the 32 months after treatments when computed tomography scan, [¹⁸F]fluoro-D-glucose positron emission tomography/computed tomography and pelvic magnetic resonance imaging showed the appearance of a lesion in the left perineal muscle suspected for recurrence. Patient was symptomless. Cytology of the suspected lesion confirmed SV adenocarcinoma recurrence. The combined approach, using radiological and nuclear medicine techniques, seems to be effective in the follow-up of SV adenocarcinoma. Technological advances, together with awareness of this rare tumor, have the potential of improving patients outcomes not only by providing earlier detection and accurate staging, but also by detecting recurrence and thereby avoiding delays and therapeutic dilemmas.

Differentiated thyroid cancer: a new perspective with radiolabeled somatostatin analogues for imaging and treatment of patients

BACKGROUND

The expression of somatostatin receptors (SSTR) in thyroid cells may offer the possibility to identify metastatic lesions and to select patients for peptide receptor radionuclide therapy (PRRT). We investigated (68)Ga-DOTATOC positron emission tomography/computed tomography (PET/CT) to select patients with progressive differentiated thyroid cancer (DTC) for PRRT as well as treatment response and toxicity in treated patients.

METHODS

We enrolled 41 patients with progressive radioiodine-negative DTC (24 women and 17 men; mean age=54.3 years, median=59 years, range=19-78 years). In all patients, [(18)F]FDG-PET/CT was performed to determine recurrent disease with enhanced glucose metabolism, and (68)Ga-DOTATOC PET/CT was used to identify SSTR expression. Dosimetric evaluation was performed with (111)In-DOTATOC scintigraphy. Eleven patients were treated with PRRT receiving a fractionated injection of 1.5-3.7 GBq (90)Y-DOTATOC/administration. Serial (68)Ga-DOTATOC PET/CT scans were performed in all treated patients to evaluate treatment response. Parameters provided by (68)Ga-DOTATOC PET/CT were analyzed as potential therapeutic predictors to differentiate responding from nonresponding. In all treated patients, adverse events and toxicity were recorded.

RESULTS

(68)Ga-DOTATOC PET/CT were positive in 24/41 of radioiodine-negative DTC patients. Based on the high expression of SSTR detected by (68)Ga-DOTATOC PET/CT, 13 patients were suitable for PRRT. Two out of 13 patients were not treated due to the lack of fulfillment of other study inclusion criteria. PRRT induced disease control in 7/11 patients (two partial response and five stabilization) with a duration of response of 3.5-11.5 months. Objective response was associated with symptoms relief. Functional volume (FV) over time obtained by PET/CT was the only parameter demonstrating a significant difference between lesions responding and nonresponding to PRRT (p=0.001). Main PRRT adverse events were nausea, asthenia, and transient hematologic toxicity. One patient experienced permanent renal toxicity.

CONCLUSIONS

In our series, SSTR imaging provided positive results in more than half of the cases with radioiodine-negative DTC, and about one third of patients were eligible for PRRT. (68)Ga-DOTATOC PET/CT seems a reliable tool both for patient selection and evaluation of treatment response. In our experience, FV determination over time seems to represent a reliable parameter to determine tumor response to PRRT, although further investigations are needed to better define its role.

PET and PET/CT with 68gallium-labeled somatostatin analogues in Non GEP-NETs Tumors

Somatostatin (SST) is a 28-amino-acid cyclic neuropeptide mainly secreted by neurons and endocrine cells. A major interest for SST receptors (SSTR) as target for in vivo diagnostic and therapeutic purposes was born since a series of stable synthetic SST-analouges PET became available, being the native somatostatin non feasible for clinical use due to the very low metabolic stability. The rationale for the employment of SST-analogues to image cancer is both based on the expression of SSTR by tumor and on the high affinity of these compounds for SSTR. The primary indication of SST-analogues imaging is for neuroendocrine tumors (NETs), which usually express a high density of SSTR, so they can be effectively targeted and visualized with radiolabeled SST-analogues in vivo. Particularly, SST-analogues imaging has been widely employed in gastroenteropancreatic (GEP) NETs. Nevertheless, a variety of tumors other than NETs expresses SSTR thus SST-analogues imaging can also be used in these tumors, particularly if treatment with radiolabeled therapeutic SST-analouges PET is being considered. The aim of this paper is to provide a concise overview of the role of positron emission tomography/computed tomography (PET/CT) with (68)Ga-radiolabeled SST-analouges PET in tumors other than GEP-NETs.

[Endovascular treatment of pararenal aortic aneurysms]

Endovascular procedures have emerged as an attractive alternative technique for the repair of abdominal aortic aneurysms with an increasing popularity and diffusion. Even if technology progresses are developing more and more efficient grafts and devices, at the moment the endovascular treatment is still not applicable to all patients. The most common reason for patient exclusion remains an unsuitable proximal implantation site. Endografts with suprarenal fixation were studied for solving the problem of the proximal neck but results seem to be not so encouraging. At the moment pararenal aortic aneurysms, involving ostia of renal or visceral arteries, are usually excluded from endovascular treatment. The solution could be a custom-made graft for each single patient, with fenestrations or branches for renal and visceral arteries. The first clinical use of a fenestrated graft was by Park in 1996 and some groups are now studying different kinds of grafts, both in experimental and clinical studies, which are opening attractive new possibilities. At present results are only preliminary but this would be the first step towards the potential substitution of the entire aorta through endovascular techniques.