Role of 18F-dopa PET/CT imaging in the management of patients with 111In-pentetreotide negative GEP tumours

Purpose To assess whether F-18-dopa PET/CT is able to provide information relevant in changing the clinical management of patients with gastro-enteropancreatic (GEP) tumours where there is negative or inconclusive conventional radiological imaging (ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI)) and In-111-pentetreotide scintigraphy. Materials and methods From January 2005 to October 2006, 84 patients with clinical and biochemical suspicion of GEP tumours were investigated by US and CT scans, MRI and In-111-pentetreotide scintigraphy. In 13/84 (15.4%) both conventional radiological imaging and In-111-pentetreotide scintigraphy provided negative or inconclusive findings, and patients were referred for 18 F-dopa PET/CT imaging. Each patient received 5.3 M Bq (.) kg(-1 18)F-dopa intravenously, and imaged 60 min later using a hybrid PET/CT scanner. Results F-18-dopa PET/CT detected the primary tumour in all 13 patients (size range, 7-26 mm, mean, 18 mm; SUV,a range, 2.3-16.3, mean, 5.7) and further 12 unsuspected lesions (size range, 12-23mm, mean 17; SUVmax range 2.8-12.7, mean 4.6). Confirmation of the PET/CT findings was obtained in all patients from histopathological analysis of tissue obtained after surgery and/or biopsy. All the F-18-dopa-positive primary lesions were confirmed as being the primary tumour at histology, whereas of the other 12 unsuspected F-18-dopa-positive lesions, 11 were found to be metastatic deposits and one due to unspecific inflammation (one false positive result). Notably, the results of F-18-dopa PET/CT imaging changed the clinical management in 11/13 patients (84%). Conclusions Our preliminary results suggest that F-18-dopa PET/CT has a promising role in GEP patients with negative or inconclusive findings at conventional radiological imaging and In-111-pentetreotide scintigraphy. The findings were helpful in biopsy guidance and played a major role in changing the management of those patients.