In general, there are three types of imaging tests most frequently used for detection, staging, and follow up of patients with neuroendocrine tumors. The first two, CT and MRI scans are the same imaging modalities commonly used in patients with all types of tumors. (Ultrasound imaging is of limited use for staging but may be used for specific purposes; e.g., needle directed biopsy.)
The Gallium-68 Dotatate PET/CT Scan is a relatively new imaging test, specific for NET detection with higher sensitivity and specificity than CT and MRI imaging. (Since the Gallium-68 scan was FDA approved and has become widely available, it has essentially replaced the Indium-111 Octreotide SPECT Scan.) Compared to the In-111 Octreotide Scan, Gallium-68 scanning is more sensitive and specific and it delivers a much lower radiation dose and is completed the same day as the injection. More more information click here.
Things to consider before getting a Gallium-68 Scan (editorial comments):
1. How might the findings affect treatment decisions? For example, if you have known metastatic disease; e.g., in your liver, and no known other sites of disease, will the treatment decisions you are currently considering be different if other areas of tumor are detected? Drug therapies (oral or injected agents) will treat all lesions in your body; having the scan may not change the drug treatment decision. If you are considering a surgical option; e.g., surgical removal of multiple liver lesions, will the surgery still be recommended if a Gallium-68 scan shows lesions at other sites outside the liver; e.g., bone or soft tissue?
2. If you have an unknown primary tumor the effectiveness of Ga-68 Scanning was reported in two sub-groups of patients:
Group One: Suspected NET based on symptoms or elevated serotonin and other imaging studies don't show a tumor. In this (small) group the Gallium 68 scans didn't detect a primary.
Group Two: Known NET tumor (metastatic disease) but no known primary. In this group the Gallium-68 scan detected a primary tumor in about 70% of cases.
3. If it is important for you to know the extent of your disease, then a Gallium-68 scan is the most sensitive and specific imaging study.
Gadoxetic acid (Eovist) Contrast Agent
Eovist is the preferred MRI contrast agent for detection/evaluation of liver metastases. If you are having an MRI for detection or follow up of liver NET lesions, your ordering physician should request Eovist as the MRI contrast agent. For more information click here.