Contribution of 111In-pentetreotide SPECT/CT imaging to conventional somatostatin receptor scintigraphy in the detection of neuroendocrine tumours

Abstract

The aim of the study was to assess the contribution of 111In-pentetreotide single-photon emission computed tomography/computed tomography (SPECT/CT) imaging to conventional somatostatin receptor scintigraphy (SRS) in terms of lesion characterization and localization in the detection of neuroendocrine tumours (NETs). A total of 107 patients with suspected or confirmed NET underwent SRS and SPECT/CT after the injection of 148-222 MBq of 111In-pentetreotide. SRS and SPECT/CT images were interpreted independently. Each site of abnormal tracer uptake was recorded according to the anatomical localization, and as being consistent or not with NET. The findings were confirmed with pathological and/or clinical/imaging follow-up data. A final diagnosis of NET was achieved in 49/107 patients (45.8%). No evidence of NET was found in the rest. SPECT/CT resulted in a significant reduction of indeterminate cases [14/107 (13.1%) vs. 1/107 (0.9%); P<0.001] and correctly reclassified one patient as negative for NET and another as positive for NET. SPECT/CT had 87.8% sensitivity and 96.6% specificity on a patient-based analysis, statistically higher than SRS (P<0.001). A total of 160 foci were detected (108 NETs and 52 physiological/benign tumours). SRS correctly classified 105/160 foci (65.6%) and remained inaccurate for 55 lesions. These 55 included 31 indeterminate lesions, 12 lesions detected only by SPECT/CT and 12 false-positive lesions. The number of foci correctly classified on the SPECT/CT images was 151/160 (94.4%), whereas two remained indeterminate and seven were false-positive findings. SPECT/CT provides incremental diagnostic value over SRS, mainly because of a precise anatomical localization that helps discriminate between tumour lesions and physiological uptake. SPECT/CT may detect unsuspected lesions in a small proportion of patients.