Diagnostic Performance of Somatostatin Receptor PET/CT Using 68Ga-DOTANOC in Gastrinoma Patients with Negative or Equivocal CT Findings

Purpose: Contrast-enhanced CT (CECT) is a standard investigative procedure in the localization of gastrinomas. Small tumors are often missed and metastatic lesions may remain occult on CT. The purpose of present study was to prospectively evaluate the diagnostic performance of (68)Ga-labeled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-NaI(3)-Octreotide ((68)Ga-DOTANOC) positron emission tomography/computed tomography (PET/CT) in gastrinoma patients with negative or equivocal CT findings.

Methods: Twenty-five patients (age 46.6 ± 13.3 years; male 60%) with clinical/biochemical diagnosis of gastrinoma and negative or equivocal findings on CECT were prospectively evaluated. All of them underwent (68)Ga-DOTANOC PET/CT which was evaluated by two nuclear medicine physicians in consensus. Combination of histopathology, serum gastrin, endoscopy, and follow-up imaging were taken as reference standard.

Results: (68)Ga-DOTANOC PET/CT was positive in 17 patients and negative in 8 patients, yielding an overall detection rate of 68%. It was positive 13/20 patients who underwent baseline evaluation and in 4/5 post-treatment patients. Of the 11 patients who had a negative CT result, (68)Ga-DOTANOC PET/CT was positive in four cases (detection rate 36.4%), while it was abnormal in 13/14 patients who had equivocal CT findings (detection rate 92.8%). Diagnostic performance of (68)Ga-DOTANOC PET/CT was superior in patients with equivocal CECT findings than that in patients with negative CECT (P = 0.010).

Conclusion: (68)Ga-DOTANOC PET/CT appears to be useful in patients with gastrinoma with negative or equivocal results on CECT, especially the latter group.