Computed Tomographic Studies of Noncalcified Nodules Related to Neuroendocrine Lung Tumor Using 68Gallium-Tagged Somatostatin Variant for Improvement in Diagnosis: A Non-Experimental, Non-Randomized, Cross-Sectional Study

BACKGROUND: 18Fluoro-fluorodeoxyglucose (FDG)- based positron-emission computed tomography (PET) has less specificity for noncalcified nodules (NNs). Somatostatin receptors affect the expression of normal and malignant cells. The purpose of the study was to compare the sensitivity, specificity, and accuracy of 68Gallium-tagged DOTA-octreotate (Ga-tDO) with that of FDG PET for diagnosis of newly detected and/or untreated NNs in lung cancer patients.
MATERIAL AND METHODS: A total of 45 patients with lung cancer were included in the cross-sectional study and underwent Ga-tDO and FDG PET. We further confirmed observed outcomes by testing immune histochemical staining for subtype 2A of somatostatin receptor in a granuloma tissue array. The chi-square test was performed for sensitivity and specificity of predictive values among the 3 diagnostic modalities. McNemar’s test was performed to compare accuracy between Ga-tDO and FDG PET. Results were considered significant at 95% confidence level.
RESULTS: Ga-tDO had less sensitivity (69% vs. 89%) but more specificity (91% vs. 78%) than FDG PET. Ga-tDO and FDG PET were characterized as 36 and 6 and in 36 and 3 lesions as accurate and inaccurate, respectively. There was an insignificant difference between Ga-tDO and FDG PET regarding diagnostic accuracy (p=0.7). Dosimetry results showed that the lungs were one of the least critically affected organs.
CONCLUSIONS: Ga-tDO was more specific but less sensitive than FDG PET scanning and imaging.

Keywords: Contrast Media, Contrast Sensitivity, Lung Neoplasms, Tomography, Emission-Computed