Biodistribution and radiation dosimetry of a novel 18F-fluoroethyl triazole [Tyr3] octreotate analogue for PET imaging in patients with advanced neuroendocrine tumours.
1Department of Syrgery and Cancer, imperial College, London, UK,2Imanova centre for imaging studies, London, UK,3Department of Radiology/ Nuclear medicine, imperial College, London, UK,4Department of Surgery ,imperial College Healthcare NHS Trust, London, UK,5Deaprtment of medicine, Imperial College, London, UK
Neuroendocrine tumours (NETs) are a heterogeneous group of neoplasms. Despite advances, detection and quantification of NET activity by imaging remains a challenge, with no universally accepted imaging standard. We present the first in-man study of 18F-fluoroethyl triazole [Tyr3] octreotate (18F-FET-?AG TOCA) in NET patients to evaluate biodistribution, dosimetry, and safety.
18F-FET-?AG TOCA was synthesized via the click reaction (Iddon L et al, 2011). Nine patients (6 female , 3 male) were enrolled into study. Eight patients with sporadic NET and 1 MEN1 syndrome. Mean age 56 yr (range 35-73 yr) and weight 75.2kg (91.2-66.3 kg). Safety data was collected during and 24 hours post tracer administration. Patients underwent whole body PET-CT multi-bed scanning over 4 hours and venous blood samples taken at specific intervals to measure 18F radioactivity concentration in blood and plasma. Regions of interest were drawn, to derive individual and mean organ residence times; effective dose (ED) was calculated with OLINDA 1.1.
All patients tolerated 18F-FET-?AG TOCA with no adverse events. Over 60% parent tracer was present in plasma at 60 minutes. High tracer uptake was observed in tumours (primary and metastases). Physiological uptake was seen in pituitary, salivary, thyroid and spleen, with low background uptake in liver, an organ where metastases commonly occur. The organs receiving highest absorbed dose were gallbladder, spleen, stomach, liver, kidneys and bladder. The calculated ED over all subjects was 0.029mSv/MBq (SD ± 0.004).
We present the first in-man study of 18F-FET-?AG-TOCA. The favourable safety, imaging and dosimetric profile makes it a valuable candidate in staging and management of NETs. Clinical studies in an expanded cohort are ongoing to clinically qualify this agent.