SPECT/CT with ^99mTc-Tectrotide in the diagnosis of insulinoma

BACKGROUND: Insulinoma is a pancreatic neuroendocrine tumor that manifests by impaired carbohydrate metabolism with the development of hypoglycemic syndrome. The instrumental methods used at the present stage do not always make it possible to identify a tumor; moreover, the data obtained often contradict each other. Thus, the search for new possibilities of visualization of insulinoma is relevant.

AIM: Evaluation of diagnostic effectiveness of scintigraphy with single-photon emission computed tomography combined with X-ray computed tomography (SPECT/CT) with ^99mTc-Tectrotide for insulinoma in a Russian cohort of patients.

MATERIALS AND METHODS: A single-centre (Endocrinology Research Centre of the Ministry of Health of the Russia), experimental, single-stage, controlled study. In the years 2017–2021 patients with pancreatic insulinoma (group 1) and hyperinsulinemic hypoglycemia of a different genesis (group 2) with negative or contradictory results of the 1st line imaging methods (ultrasound, magnetic resonance imaging (MRI), computed tomography (CT)) were included. All participants underwent the whole-body scintigraphy and low-dose SPECT/CT with ^99mTc-Tectrotide (500–900 MBq). The studies were performed on a tomograph of the SPECT/GE Discovery NM/CT 670 using low-energy high-resolution collimators (LEHR) in the «whole body» mode.

RESULTS: In the group 1 (n=21), according to the results of a pathomorphological study, the presence of 26 insulin-producing tumors was confirmed. Group 2 included 9 patients. According to the SPECT/CT with ^99mTc-Tectrotide, 14 tumors were diagnosed in group 1 out of 26 insulin-producing tumors of the pancreas, and negative results were obtained in group 2 in 100% of cases. Thus, the sensitivity and specificity of the method were: 54%, 95% CI [33%; 73%] and 100%, 95% CI [68%; 100%], respectively.

CONCLUSION: SPECT/CT with ^99mTc-Tectrotide can detect insulinoma in 54% of cases with negative or contradictory results of 1st-line imaging methods (ultrasound, MRI, CT). This study can be effectively used as an alternative to SPECT/CT with ¹¹¹In-octreotide, as a 2nd-line method for topical search for an insulin-producing pancreatic tumor.

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