Somatostatin Receptor Scintigraphy
A nuclear medicine imaging technique using radiolabelled somatostatin analogues to detect tumours that overexpress somatostatin receptors. This technique identifies neuroendocrine tumours suitable for somatostatin analogue therapy or peptide receptor radionuclide therapy with lutetium Lu-177 dotatate.
Technical Context
OctreoScan (111In-pentetreotide/111In-DTPA-octreotide): radiolabelled octreotide analogue imaged by gamma camera/SPECT. Sensitivity: approximately 70-90% for well-differentiated NETs (lower for G3 NETs and insulinomas which may have lower SSTR expression). OctreoScan was the standard imaging for NETs before Ga-68 DOTATATE PET/CT became available. Ga-68 DOTATATE PET/CT advantages: higher spatial resolution (PET vs SPECT), higher sensitivity (>90% vs ~80%), lower radiation dose (Ga-68 shorter half-life), same-day imaging (vs 24-48 hour delay with 111In), and quantitative uptake measurement (SUV values predicting PRRT response). OctreoScan remains available where PET/CT is unavailable but is being replaced by Ga-68 DOTATATE PET/CT as the standard of care for NET imaging worldwide.