Background and objective: 111In-DPTA-Octreotide (Octreoscan) has limited spatial resolution and a somewhat lower receptor affinity of the radiopeptide compared to DOTATATE, a novel somatostatin analogue, which can be radiolabelled with 68Ga and adapted for PET imaging, resulting in an increased spatial resolution. The aim of this study was to evaluate the diagnostic performance of 68Ga-DOTATATE PET in patients with NET and to compare this tecnique with Octreoscan.
Patients and methods: Fifty-seven patients with NET were enrolled, located in pancreas (27), duodenum/ileum (4), lung (7), stomach (6), thyroid (12), paraganglia (1). Forty patients had a sporadic and 17 a MEN1-related NET. 68Ga-DOTATATE PET was performed in all cases by acquiring whole body studies 4060 min after the radioligand i.v. injection (range 74111 MBq). Octreoscan was also performed in a subgroup of 27 patients using intravenous injection of Indium-111-DTPA-Phe1-octreotide (Octreoscan, Mallinckrodt Medical, Petten, The Netherlands; 120200 MBq). At the time of PET/Octreoscan evaluation 40 patients had tumor lesions and 17 were negative as confirmed by CT/MR examination and clinical follow-up.
Results: The patient based sensitivity was 77% with a specificity of 100% while the lesion based sensitivity was 64% with a specificity of 85%. Positive and negative predictive values were 100 and 65% respectively. The sensitivity of PET was about 100% in pancreatic and gut NET, about 75% in lung and thyroid NET and lower than 50% in gastric NET. In a subgroup of 27 patients undergone both PET and Octreoscan, the result was concordant in 21 and discordant in six cases. The discordant results included five PET positive and Octreoscan negative NET (three pancreatic NET, two medullary thyroid cancer) and one PET negative and Octreoscan positive NET (an atypical bronvhial carcinoid).
Conclusions: 68Ga-DOTATATE PET shows high sensitivity and excellent specificity in patients with NET, revealing a higher diagnostic performance than Octreoscan.
30 Apr - 04 May 2011
European Society of Endocrinology