Incremental Value of 111-In Pentetreotide SPECT/CT Fusion Imaging of Neuroendocrine Tumors

Rationale and Objectives

Hybrid single photon-emission computed tomographic (SPECT) and computed tomographic (CT) imaging for the investigation of neuroendocrine tumors allows the fusion of functional and anatomic information in a rapid and efficient method. The aim of this study was to assess the incremental diagnostic value of ¹¹¹In pentetreotide SPECT/CT imaging compared with traditional planar and SPECT imaging with respect to lesion localization and characterization and reader confidence.

Materials and Methods

Forty-nine patients (23 male, 26 female; mean age, 56.9 years; range, 14–88 years) who underwent ¹¹¹In pentetreotide planar, SPECT, and SPECT/CT imaging were eligible for this retrospective study, including patients with suspected or confirmed carcinoid tumors (n = 24), endocrine pancreatic tumors (n = 18), medullary thyroid cancer (n = 3), paragangliomas (n = 2), and multiple endocrine neoplasia type I (n = 2). Planar and SPECT images were reviewed by two blinded readers, followed by interpretation using additional SPECT/CT images in a subsequent session. A third reader provided consensus in cases with disagreements.

Results

In 55 of 89 lesions (61.8%), ¹¹¹In pentetreotide SPECT/CT imaging improved lesion localization compared to planar and SPECT imaging; in 25 of 89 lesions (28.1%), SPECT/CT imaging changed lesion classification. In 20 of 49 patients (40.8%) for reader 1 and 14 of 49 patients (28.6%) for reader 2, ¹¹¹In pentetreotide SPECT/CT imaging provided incremental diagnostic value, which was considered likely to affect patient management in twelve of 20 and seven of 14 patients, respectively. Increased reader confidence was found in 32 of 49 patients (65.3%) for both readers with uniformly high confidence after SPECT/CT interpretation.

Conclusions

Hybrid ¹¹¹In pentetreotide SPECT/CT imaging provides incremental diagnostic value and greater reader confidence over planar and SPECT imaging. This is achieved though superior lesion localization, the identification of physiologic activity, and additional anatomic information derived from the nondiagnostic CT portion of the study.

Key Words: Neuroendocrine tumors, SPECT/CT, ¹¹¹In pentetreotide scintigraphy