If you take a GLP-1 agonist medication, you might be curious about the warning on the label about not using the medication if you or anyone in your family has ever had medullary thyroid cancer (MTC). (Speak with your health care provider about whether any of your medicines include this warning.)
What is MTC and is it something you need to be worried about?
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What is medullary thyroid cancer?
Medullary thyroid cancer is a rare type of cancer, accounting for 1% to 2% of thyroid cancers in the United States, according to the American Thyroid Association. Other types of thyroid cancers occur in thyroid follicular cells, which are cells that make thyroid hormone. MTC originates in parafollicular C-cells of the thyroid gland. Rather than making thyroid hormone, these cells make a hormone called calcitonin. Calcitonin regulates the amount of calcium and phosphate in the blood, opposing the action of parathyroid hormone.
MTC is inherited, meaning it can run in the family in up to 25% of cases. Inherited MTC can also be associated with other types of endocrine tumors, including those found in Multiple Endocrine Neoplasia (MEN) 2A and MEN 2B.
MTC frequently spreads to the lymph nodes and from there, can spread to the brain, lungs, liver, and bones. Early detection and treatment are crucial.
What are the symptoms of medullary thyroid cancer?
Here are common signs and symptoms of MTC:
- A lump or nodule in the thyroid. A person may notice the lump themselves or it might be discovered during a routine physical exam or an imaging test, such as a CT scan.
- Pain in the neck, jaw, or ear.
- Hoarseness. This may occur if the thyroid tumor is blocking the vocal cords.
- Difficulty swallowing or breathing. This can happen if the tumor is pressing on the esophagus or the windpipe.
- Diarrhea. Diarrhea can occur due to increased levels of calcitonin.
How is medullary thyroid cancer diagnosed?
“MTC is diagnosed by your doctor first feeling your throat to check for a lump, followed by imaging scans of the thyroid,” says the National Cancer Institute’s Center for Cancer Research. Imaging might include ultrasound, a CT scan, or an MRI.
In addition, a biopsy of your thyroid will likely be done using a very fine needle. A pathologist will look at the tissue under a microscope to check for cancer cells and to determine what type of thyroid cancer it is.
Your doctor may order blood tests to measure the amount of calcitonin and carcinoembryonic antigen (CEA) in the blood — these proteins are typically elevated with MTC and can help confirm the diagnosis, as well. Also, these two proteins serve as tumor markers during follow up after treatment to detect any remaining cancer or recurrence of cancer.
How is medullary thyroid cancer treated?
The main treatment for MTC is the removal of the thyroid gland (called a thyroidectomy). People with a high risk of MTC, meaning people who carry a certain gene, may have a thyroidectomy to help prevent MTC. If the cancer has spread to the lymph nodes in the neck or upper chest, these may be removed, as well. After surgery, the person will need to take thyroid replacement hormone for the rest of their life.
If MTC has spread beyond the neck, surgery may be more palliative, or aimed at reducing complications rather than completely eliminating the tumor, says the American Thyroid Association. Radiation or chemotherapy may be use along with surgery. It’s recommended that a thyroid cancer surgeon who has experience with MTC perform surgery, since MTC is rare and many thyroid surgeons rarely see or treat people with this type of thyroid cancer.
Two chemotherapeutic agents, vandetanib (brand name Caprelsa) and cabozantinib (CABOMETYX), have been approved by the FDA for use in patients with MTC. These drugs don’t cure advanced cancer that has spread, but they can slow down or partially reverse the growth of the cancer.
What is the follow-up after medullary thyroid cancer treatment?
If you are diagnosed with and treated for MTC, you will need regular examinations, as this type of cancer can return, even years later. A return visit will include a physical examination, especially of the neck, and will likely include a neck ultrasound to check for lumps, nodules, or enlarged lymph nodes that could indicate that the cancer has returned.
You will also need blood tests to check your levels of thyroid stimulating hormone (TSH), since you will be taking thyroid hormone replacement and may need a dose adjustment. In addition, levels of calcitonin and CEA should be checked. If calcitonin is detected in the blood, it could be a sign that the cancer has recurred, according to the National Library of Medicine.
What is the prognosis for someone with medullary thyroid cancer?
The prognosis if you have MTC depends on many factors, including:
- If the cancer has spread to other parts of the body
- If the cancer responds to chemotherapy
- How much of the tumor was removed during surgery
If MTC is detected and treated early, surgery can be a cure. But even if it’s not caught early, MTC tends to be slow to progress. Blood levels of calcitonin or CEA over the first year after surgery can also help to predict survival. Be sure to talk with your doctor about your own prognosis.
GLP-1 agonists and medullary thyroid cancer
GLP-1 agonist medications are contraindicated in people who have MTC, a family history of MTC, or a condition called Multiple Neoplasia Syndrome type 2 (MEN 2). Be sure to let your doctor know if you have either of these conditions or a family history of MTC and discuss the risks and benefits of taking a GLP-1 agonist medication.
For more information about thyroid cancer, visit the National Cancer Institute website.
Want to learn more about keeping your thyroid healthy? Read “Diabetes and Thyroid Conditions.”