Comparison of ⁶⁸Ga-DOTATATE and ⁶⁸Ga-DOTANOC PET/CT imaging in the same patient group with neuroendocrine tumours.

PURPOSE: Recent studies have suggested that positron emission tomography (PET) imaging with (68)Ga-labelled DOTA-somatostatin analogues (SST) like octreotide and octreotate is useful in diagnosing neuroendocrine tumours (NETs) and has superior value over both CT and planar and single photon emission computed tomography (SPECT) somatostatin receptor scintigraphy (SRS). The aim of the present study was to evaluate the role of (68)Ga-DOTA-1-NaI(3)-octreotide ((68)Ga-DOTANOC) in patients with SST receptor-expressing tumours and to compare the results of (68)Ga-DOTA-D-Phe(1)-Tyr(3)-octreotate ((68)Ga-DOTATATE) in the same patient population.

METHODS: Twenty SRS were included in the study. Patients' age (n = 20) ranged from 25 to 75 years (mean 55.4 ± 12.7 years). There were eight patients with well-differentiated neuroendocrine tumour (WDNET) grade1, eight patients with WDNET grade 2, one patient with poorly differentiated neuroendocrine carcinoma (PDNEC) grade 3 and one patient with mixed adenoneuroendocrine tumour (MANEC). All patients had two consecutive PET studies with (68)Ga-DOTATATE and (68)Ga-DOTANOC. All images were evaluated visually and maximum standardized uptake values (SUV(max)) were also calculated for quantitative evaluation.

RESULTS: On visual evaluation both tracers produced equally excellent image quality and similar body distribution. The physiological uptake sites of pituitary and salivary glands showed higher uptake in (68)Ga-DOTATATE images. Liver and spleen uptake values were evaluated as equal. Both (68)Ga-DOTATATE and (68)Ga-DOTANOC were negative in 6 (30 %) patients and positive in 14 (70 %) patients. In (68)Ga-DOTANOC images only 116 of 130 (89 %) lesions could be defined and 14 lesions were missed because of lack of any uptake. SUV(max) values of lesions were significantly higher on (68)Ga-DOTATATE images.

CONCLUSION: Our study demonstrated that the images obtained by (68)Ga-DOTATATE and (68)Ga-DOTANOC have comparable diagnostic accuracy. However, (68)Ga-DOTATATE seems to have a higher lesion uptake and may have a potential advantage.