Updated on April 10, 2025.
Gastroenteropancreatic neuroendocrine tumors (GEP-NETS) are a type of cancer that begins in the neuroendocrine cells of the pancreas or gastrointestinal tract. Neuroendocrine cells are a type of hormone producing cell that link the body’s nervous system and endocrine (hormone-producing) system—neuroendocrine cells receive signals from the nervous system, and in response to those signals, produce and release hormones. GEP-NETs begin when these cells undergo mutations and begin to grow out of control.
How are GEP-NETs diagnosed?
The process of diagnosing GEP-NETs will involve multiple tests, including:
- A physical exam and medical history, including symptoms a person is experiencing
- Blood and urine tests to measure hormone levels and tumor markers (substances that indicate the presence of a tumor)
- Imaging tests (such as CT scan, MRI, PET scan, endoscopy, and potentially others) will be used to determine the size and location of the tumor, as well as any areas of the body where the cancer has spread
- A biopsy, where a sample of tissue from the tumor is examined under a microscope
Staging
Based on the information gathered in diagnosis, a GEP-NET will be given a stage. GEP-NETs are staged using the TNM staging system. TNM stands for "tumor, node, metastasis."
- Tumor refers to the size of the tumor and if it has grown into nearby tissues
- Node refers to whether there are cancer cells in lymph nodes near the tumor
- Metastasis refers to whether the cancer has spread to distant sites in the body
Tumor grade
In addition to stage, another important piece of information is the tumor grade. When grading GEP-NETs, an important measurement is the number of cells that are in the process of dividing.
Two terms to know are well-differentiated and poorly differentiated. Well-differentiated GEP-NETs have a lower grade and are considered less aggressive. Poorly differentiated NETs have a higher grade and are considered more aggressive.
Functional vs. nonfunctional
Another important piece of information is whether the GEP-NET is functional or nonfunctional:
- Functional GEP-NETs produce excess hormones and cause symptoms related to hormone imbalances.
- Nonfunctional GEP-NETs do not produce hormones, or do not produce enough hormones to cause symptoms.
How are gastrointestinal neuroendocrine tumors treated?
Treatment will depend on the stage, location, grade, and other factors about the cancer. It will also depend on the overall health of the person being treated. The first choice in treatment for GEP-NETs is surgery to remove the tumor or as much of the tumor as possible.
Sometimes, other procedures to destroy or shrink tumors will be used, including procedures that destroy cancer cells using heat, cold, chemicals, radiation, or by blocking off blood vessels that are supplying a tumor.
Additionally, treatment can include medications:
- Somatostatin analogs (SSAs). These medications can reduce the amounts of hormones being made by a functional GEP-NET and help alleviate symptoms caused by hormone imbalances. SSAs may also slow the growth of some tumors.
- Targeted therapies. These are anti-cancer drugs that work by targeting specific features found on cancer cells, such as proteins that cancer cells need to grow and spread. Targeted therapies typically cause less damage to healthy cells compared to chemotherapy.
- Peptide receptor radionuclide therapy (PRRT). This therapy combines targeted therapy with radiation therapy. This drug works by attaching to cancer cells and delivering radioactive medications that destroy those cancer cells.
- Chemotherapy. Chemotherapy is often used in the treatment of high-grade NETs that are poorly differentiated.
It’s important to remember that there is no best treatment for GEP-NETs, only the treatment that is recommended for a specific person. Your best source of information about a diagnosis and treatment will be a healthcare provider.
