Octreoscan is used to visualize hormone-producing tumors of the nervous and endocrine systems, or neuroendocrine tumors. Most tumors of this nature contain cells with a receptor for the hormone somatostatin.

In octreoscan, octreotide, an analogue of somatostatin, is labeled with a radioactive tracer and injected intravenously; the radioactive octreotide attaches to somatostatin receptors on the tumor cells and can then be observed with a special scanning camera. A variation of nuclear scanning, called single-photon emission computed tomography, or SPECT, enhances the sensitivity of the test.

An OctreoScan may be ordered for the following purposes:

  • To identify and pinpoint the location of benign or malignant (cancerous) neuroendocrine tumors (such as carcinoid tumors, small cell lung cancer, pituitary adenoma, neuroblastoma, medullary thyroid carcinoma and islet cell tumor of pancreas) prior to their surgical removal; this test can identify both primary cancer and cancer that has metastasized (spread) from other locations
  • To monitor the effectiveness of therapy for neuroendocrine tumors and to detect recurrences or progression of disease