Octreo-SPECT/CT Imaging for Accurate Detection and Localization of Suspected Neuroendocrine Tumors

Aim: The aim of the present study was to prospectively evaluate the add value provided by [(111)In]DTPA-octreotide single-photon emission computed tomography/computed tomography (Octreo-SPECT/CT) with respect to [(111)In]DTPA-octreotide SPECT (Octreo-SPECT) in terms of diagnostic accuracy and localization of neuroendocrine tumors (NETs).

Methods: Eighty-one consecutive patients with known or suspected NET underwent [(111)In]DTPA-octreotide scintigraphy using an integrated SPECT/low-energy-CT system (Infinia & Hawkeye; GE Medical Systems, Milwaukee, WI, USA). SPECT and fused SPECT/CT images were interpreted separately and a lesion-by-lesion analysis was performed with regard to classification (probability of NET graded on a 5-point scale) and localization of each abnormal focal tracer uptake. A subgroup analysis, distinguishing between abdominal and thoracic lesions, and a patient-by-patient analysis for likelihood of NET in each patient was also performed. Standard of reference for confirming presence or absence of NET was either histopathology or clinical/imaging follow-up data. The value of SPECT/CT imaging was assessed by ROC analysis and McNemar test.

Results: A final diagnosis of NET was achieved in 43 out of 81 patients and a total of 169 areas (138 NET and 31 benign/physiological) with focal tracer uptake were included in the final lesion-by-lesion analysis. SPECT/CT imaging led to a significantly higher proportion of patients (75/81=92.6% vs 64/81=79%) and lesions (163/169=96.4% vs 138/169=81.1%) correctly classified vs SPECT alone. ROC analysis confirmed that Octreo-SPECT/CT performed significantly better than Octreo-SPECT for the detection of NET on both patient- and lesion-based analysis, improving especially evaluation of abnormal tracer uptake in the abdomen. Moreover, Octreo-SPECT/CT accurately localized 160/169 (94.7%) lesions, significantly higher than SPECT alone (77/169= 45.6%).

Conclusions: Octreo-SPECT/CT allows more accurate detection and localization of NETs than simple Octreo-SPECT, with major benefits for lesions located in the abdomen.