Tumour scintigraphy – 111In-pentetreotide (Octreoscan)

A practical guide for referring physicians

Principle and method

Scintigraphy with 111In-pentetreotide is a specific radionuclide examination aimed at detecting tumours expressing somatostatin receptors (SSTR). The radiopharmaceutical, a somatostatin analogue labelled with 111In, binds to subtype 2 and 5 receptors, which are abundantly expressed in most neuroendocrine tumours (NETs).

Imaging is performed using whole-body planar scintigraphy and targeted SPECT/CT, which increases localisation accuracy and allows even smaller lesions to be assessed.

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Main clinical indications

  • Neuroendocrine tumours (NET):
    • carcinoid, gastrinoma, insulinoma, glucagonoma, VIPoma
    • pancreatic and gastrointestinal NET
  • Pituitary tumours with somatostatin receptor expression
  • Paragangliomas, pheochromocytomas – complementary to MIBG
  • Assessment of suitability for somatostatin analogue therapy or radionuclide therapy (PRRT)

Interpretation 

  • Positive finding: pathological foci of increased accumulation in areas with high SSTR expression
  • This method is still valuable where PET scanning is not available and for assessing the extent of the disease.

Practical information for the referring physician

  • Patient preparation: no need to discontinue regular medication; for patients treated with somatostatin analogues, discontinuation before the examination is recommended (short-acting – min. 24 hours, depot – 4–6 weeks)
  • Examination duration: imaging usually takes place 4 and 24 hours after administration of the radiopharmaceutical (sometimes 48 hours), and lasts approximately 1 hour
  • Radiation exposure: 10–12 mSv
  • Contraindications: pregnancy, breastfeeding (relative)

Summary for practice:

Scintigraphy with 111In-pentetreotide (Octreoscan) is:

  • the standard method for detecting and staging neuroendocrine tumours,
  • useful for assessing the extent of the disease and monitoring treatment,
  • key for indicating PRRT or somatostatin analogue therapy,
  • despite being gradually replaced by PET methods, it remains an important tool, especially where PET is not available.