How Are Neuroendocrine Tumors Diagnosed?
Unfortunately, as a rare cancer, NETs are commonly misdiagnosed as another condition. About half of NETs are not properly diagnosed until later stages when the cancer has spread to other areas. Many carcinoid tumors are discovered incidentally during gastrointestinal surgery.
Arriving at a definitive diagnosis may require several types of tests and the expertise of several different specialists. You may undergo some of the following:
- Blood tests such as a complete blood count (CBC) and comprehensive metabolic panel
- Urine tests to assess kidney function and 5-HIAA biomarker
- Biochemical tests to measure certain substances and hormones
- Imaging tests such as CT, MRI, ultrasound and echocardiogram, endoscopic ultrasound, bronchoscopy, esophagogastroduodenoscopy and colonoscopy
- NetSpot® Scan (gallium-68 dotatate) is the latest imaging innovation that uses a radiotracer agent instead of glucose for a positron emission tomography (PET) scan and can detect small lesions and early-stage NETs significantly better than other imaging.
- Positron Emission Tomography/Computed Tomography (PET/CT) is often used to depict active cancer cells. First, you would receive an injection of a radiolabeled glucose solution. Active cells take up more of the glucose and appear brighter on the scan. However, because many neuroendocrine tumors grow slowly, they do not consume the glucose very quickly and may not appear distinctly bright.
- Octreoscan (somatostatin receptor scintigraphy) uses a radioactive tracer called In-octeotride. The tracer finds neuroendocrine cells that have receptors for somatostatin, a growth hormone, causing them to appear on images taken with a gamma camera. Images are taken 4 hours after injection with the radiotracer, again 24 hour later, and possibly 48 hours after the injection.
- Biopsy to remove a sample of tissue or fluid from the tumor to be tested and analyzed.
Typical positron emission tomography (PET) scans have limitations in detecting neuroendocrine tumors because the slow-growing cells do not consume glucose rapidly. Netspot® is a new radiotracer agent that uses gallium-68 dotatate instead of glucose. A radioactive lookalike of the hormone that binds to somatostatin receptors on neuroendocrine tumors, gallium-68 dotatate appears very distinctly on high-resolution PET scans, highlighting even very small tumors and lesions. A Netspot scan can be completed in a couple hours compared to 2 to 3 days for the octreoscan with gamma camera. In addition, patients whose NETs are detected with Netspot may be eligible for a new treatment called Peptide Receptor Radionuclide Therapy (PRRT), which uses hormone-tagged radiation to find and attack the cancer cells.