Frequently Asked Questions - OctreoScan

Are you assuming that the hot spot in your RLQ on the OctreoScan is a primary carcinoid in the appendix, which is the origin of the small, presumably metastatic lesion, in the liver ?  Very unlikely.  More likely a carcinoid originates in the terminal ileum (which is so close to the appendix that the scan cannot differentiate between the two).  Furthermore, appendiceal carcinoid only rarely spreads so far as the liver while carcinoids of the terminal ileum much more frequently do so.  But if neither was seen as a mass on the CT scan or on colonoscopy or small intestine barium X-ray series (was this done?), they would be too small for, and it would be too dangerous, to do a needle biopsy.  In short, needle biopsy of the liver is easier and safer. 

An OctreoScan can very occasionally show a carcinoid before CT scan or chemistries indicate its presence, but this situation is very infrequent. Visually it is used to help locate a tumor when chemistries show it is present and CT scan doesn't image it. Also when CT scan is positive the OctreoScan may show additional sites of the tumor not seen on CT.

Finally even when tumor is seen on a CT scan and chemistries are positive, the OctreoScan is useful because a positive result indicates the presence of SST2 receptors in the tumor and that means the patient will most likely respond well to treatment with Sandostatin and also has a better prognosis than does the patient with carcinoid tumor but a negative OctreoScan.

An OctreoScan is fairly straightforward. While it cannot give an indication as to tumor size, it can indicate the extent of disease metastasis and show possible loci for tumors which may or may not have been suspected. Essentially what happens is this: about 4 to 24 hours prior to scanning, a Nuclear tag (about 6 milliCuries) piggybacked onto a somatostatin analog (like Sandostatin) is injected.

This tag is then taken up by any tissue exhibiting a type two receptor. Usually you find type two receptors in carcinoid cancers, liymphomas, some breast cancers and so on. The body of the person is then scanned at 24, 48 and possibly 72 hours or whenever the oncologist and radiologist deem it beneficial. The tag being tumor-specific will cause any tissue with the requisite receptors to light up on the scan film. The test is sort of go or no-go.

Most carcinoid tumors have the receptors and light up the film; about 2 percent of tumors do not have the receptors and thus do not show up. If the patient is on a somatastatin medication such as Sandostatin, the receptors will be blocked and the tumors will not show up. Sandostatin has to be stopped about 3 days prior to scanning for an accurate test to be performed.

Octreoscan is the imaging technique of choice in addition to CT scan and MRI. In appropriate cases, Neotect Scan, FDG PET scan or F18 Dopa PET Scan and MIBG Scan in expert hands are useful. Measurement of urine and blood catecholamine could unmark a pheochromocytoma which causes flushing , fluctuating blood pressure and even diarrhea.

Every last trace of octreotide and the isotope Indium 111 used in the OctreoScan are gone from the body within 1 week. There is no effect on conception thereafter.

Every last trace of octreotide and the isotope Indium 111 used in the OctreoScan are gone from the body within 1 week.

The OctreoScan is a test which images 85% of carcinoid tumors but is not the best way to show their growth. It does indicate the potential usefulness of Sandostatin (octreotide) treatment when a tumor lights up on the OctreoScan.