Comparison of Diagnostic Sensitivity and Quantitative Indices Between (68)Ga-DOTATOC PET/CT and (111)In-Pentetreotide SPECT/CT in Neuroendocrine Tumors: a Preliminary Report

Purpose: In-pentetreotide has been used for neuroendocrine tumors expressing somatostatin receptors. Recently, (68)Ga-DOTATOC PET has been used with the advantage of high image quality. In this study, we compared quantitative indices between (111)In-pentetreotide SPECT/CT and (68)Ga-DOTATOC PET/CT.

Methods: Thirteen patients diagnosed with neuroendocrine tumors were prospectively recruited. Patients underwent (111)In-pentetreotide scans with SPECT/CT and (68)Ga-DOTATOC PET/CT before treatment. The number and location of lesions were analyzed on both imaging techniques to compare lesion detectability. Additionally, the maximal uptake count of each lesion and mean uptake count of the lungs were measured on both imagings, and target-to-normal lung ratios (TNR) were calculated as quantitative indices.

Results: Among 13 patients, 10 exhibited lesions with increased uptake on (111)In-pentetreotide SPECT/CT and/or (68)Ga-DOTATOC PET/CT. Scans with SPECT/CT detected 19 lesions, all of which were also detected on PET/CT. Moreover, 16 additional lesions were detected on PET/CT (6 in the liver, 9 in the pancreas and 1 in the spleen). PET/CT exhibited a significantly higher sensitivity than SPECT/CT (100 % vs. 54 %, P < 0.001). TNR was significantly higher on PET/CT than on SPECT/CT (99.9 ± 84.3 vs. 71.1 ± 114.9, P < 0.001) in spite of a significant correlation (r = 0.692, P = 0.01).

Conclusion: Ga-DOTATOC PET/CT has a higher diagnostic sensitivity than (111)In-pentetreotide scans with SPECT/CT. The TNR on PET/CT is higher than that of SPECT/CT, which also suggests the higher sensitivity of PET/CT. (111)In-pentetreotide SPECT/CT should be used carefully if it is used instead of (68)Ga-DOTATOC PET/CT.