OctreoScan (In-111 Octreotide): How It Localizes
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Question
This In-111 octreotide (OctreoScan) image shows focal abnormal uptake suspicious for a neuroendocrine tumor. What is the PRIMARY mechanism by which OctreoScan detects neuroendocrine tumors?
- APreferential glucose metabolism in neuroendocrine tumor cells
- BAccumulation in areas of increased vascularity
- CMitochondrial uptake proportional to cell membrane potential
- DBinding of radiolabeled octreotide to somatostatin receptors (SSTR2) overexpressed on NETs
Show the answer and explanation
D. Binding of radiolabeled octreotide to somatostatin receptors (SSTR2) overexpressed on NETs
In-111 octreotide (OctreoScan) is a radiolabeled somatostatin analogue that binds to somatostatin receptors, particularly SSTR2, which are overexpressed on most neuroendocrine tumors (NETs) — including carcinoid tumors, gastrinomas, insulinomas, glucagonomas, and pheochromocytomas. Normal physiologic uptake is seen in the liver, spleen, kidneys, and bowel. OctreoScan has largely been replaced by Ga-68 DOTATATE PET/CT, which has superior sensitivity and resolution.
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