Diagnostic efficiency of 68Ga-DOTATATE PET/CT as compared to 99mTc-Octreotide SPECT/CT and conventional morphologic modalities in neuroendocrine tumors

Objective(s): In view of somatostatin receptor (SSR) expression on cell membranes of the majority of neuroendocrine tumors (NETs), functional imaging exploiting analogs of SSR alongside the anatomical imaging is the mainstay of this diagnostic modality. In this prospective study, we assessed and directly compared the diagnostic parameters of 68Ga-DOTATATE PET/CT and 99mTc-Octreotide SPECT/CT, as well as CT/MRI. Methods: Twenty-five NET patients, either histologically proven or highly suspicious for NET, who were referred for Octreotide Scan were enrolled in this prospective study. They all underwent 99mTc-Octreotide SPECT/CT and then 68Ga-DOTATATE PET/CT. A blind interpretation was conducted for each imaging as well as for the previously obtained conventional imaging (CT or MRI). The patient-based and lesion-based analysis were conducted and the results of the three modalities were compared. The histopathologic confirmation or follow-up data were considered as the gold standard. Also, the impact of 68Ga-DOTATATE PET/CT on the patient’s management was assessed. Results: Overall, 77 lesions in 14 patients, 135 in 19 and 86 in 16 were detected on 99mTc-Octreotide SPECT/CT, 68Ga-DOTATATE PET/CT and CT/MRI, respectively. On patient-based analysis, the sensitivity was 65%, 90% and 71% for 99mTc-Octreotide SPECT/CT, 68Ga-DOTATATE PET/CT and CT/MRI, respectively. Also, the specificity was 80%, 80% and 75% for 99mTc-Octreotide SPECT/CT, 68Ga-DOTATATE PET/CT and CT/MRI, respectively. The correlation between 68Ga-DOTATATE PET/CT and 99mTc-Octreotide SPECT/CT results was significant (P=0.02; kappa value=0.57), no correlation, however, was depicted with CI (P=0.07; kappa value=0.35). On lesion-based analysis, 68Ga-DOTATATE PET/CT found more organs (P=0.02) and lesions (P=0.001) in comparison with 99mTc-Octreotide SPECT/CT and also more lesions in comparison with CT/MRI (P=0.003). In addition, comparing with 99mTc-Octreotide SPECT/CT and CT/MRI, 68Ga-DOTATATE PET/CT revealed more data in 44% and 36% of the patients, resulting in management modification in 24% and 20%, respectively. Conclusion: Comparing with 99mTc-Octreotide SPECT/CT and CT/MRI, 68Ga- DOTATATE PET/CT provided more sensitivity and specificity in patients with NETs showing more involved organs as well as tumoral lesions. Also, 68Ga-DOTATATE PET/ CT led to change of management in up to one-fourth of the patients, especially in a sub-group re-evaluated for recurrence.