MIBG SCAN (also called a metaiodobenzylguanidine scan)

The MIBG scan uses a substance (metaiodobenzylguanidine) that is attracted to neuroendocrine cells. When MIBG is bound to a radioactive material, usually a radioactive isotope of iodine-123, it can help identify certain types of tumours throughout the body. Similar to the OctreoScan, MIBG technology is used to treat, diagnose and monitor patients with NETs. Frequently, an MIBG scan is used to confirm the presence of pheochromocytoma or neuroblastoma tumours and is helpful in identifying patients who are not candidates for surgery but might benefit from targeted radionucleotide therapy instead.

Having an MIBG scan is a two-part process: first, the MIBG is injected and, after a period of 24 hours, the scan is performed. This delay is necessary to allow the tumour adequate time to accumulate the MIBG, enabling it to be seen on an imaging screen.

After being injected into the bloodstream, approximately 40% to 85% of functioning malignant NETs will accumulate the MIBG. The ability of a tumour to “take up” the MIBG is referred to as being “MIBG-avid,” and this ability varies widely depending on the type of the primary tumour. For example, if a primary tumour is located in the pancreas, metastatic tumours will rarely show up on an MIBG scan.

When an MIBG procedure is used to deliver treatment to a tumour, it is attached to a different type of radioactive isotope of iodine, commonly iodine-131. Treatment is often administered at three- to six-month intervals but protocols may differ between cancer treatment centres.