Calcitonin doubling time is the amount of time (usually in either months or years) that it takes for a patient’s calcitonin to double in amount. It is calculated using levels of calcitonin in the blood over multiple time points, usually using no less than two years of levels to calculate. The shorter the doubling time, often the faster the MTC is thought to be growing. Of note, calcitonins should only be used in CDT or compared to one another if they were performed at the same lab.

Typically, calcitonin level does correlate with extent of disease where, when calcitonin is over 500, there is a higher chance that there is disease outside of the neck like lungs, liver, or bones. However, there are times when the medullary thyroid cancer does not produce calcitonin effectively, in which case the calcitonin may seem lower even in the setting of distant metastasis. In this situation, we also look at the CEA level which is typically much lower than the calcitonin level, but if the CEA is somewhat similar to the calcitonin level, that might suggest a dedifferentiated MTC. The higher the calcitonin level, usually the more disease is present.

Stage is determined by the extent of disease seen on imaging and pathology. Your physician should be able to tell you your stage of disease.

Staging is described through the TNM classification system and is made up of looking at the primary tumor (described as the T), whether the disease has spread to the lymph nodes (described as the N), and whether the cancer has spread to distant parts of the body (described as M).

A “center of excellence” is an institution that has health care providers with extensive experience in treating MTC. There is not a certification for an MTC center of excellence; however, it is a place that treats a high number of patients with this rare disease.

Patients are considered cured if they have no evidence of disease on imaging or in evaluation of the tumor markers in their blood. However, we continue to follow such patients because recurrence is always possible in the future.

If a patient has an RET gene mutation/change that causes hereditary medullary thyroid cancer, they also are at risk for developing pheochromocytoma and primary hyperparathyroidism. Therefore, they would be tested annually for these two diseases. Usually this testing is a blood test but sometimes can be a urine test.

All tumors and cancer are caused by changes in genes. These changes are called mutations. In patients with an inherited disease like MEN2, the disease-causing mutation is in every cell of the body when they are born, and this is called a germline mutation. Sometimes mutations occur only within the tumor or cancer itself. These mutations are called somatic mutations and are acquired over time. Somatic mutations are not present from birth nor can they be passed down to the next generation. Germline mutations are typically detected through a blood or saliva test, while somatic mutations are detected by evaluation of the tumor tissue itself.

25% of MTC is hereditary (runs in families). The first step is to determine whether you have a hereditary cancer syndrome through genetic testing. Individuals with a known hereditary cancer syndrome, such as MEN2, may choose to use preimplantation genetic diagnosis, or PGD, to ensure they won’t pass the hereditary syndrome on to their children. PGD is the process of performing genetic testing on embryos for a known hereditary cancer syndrome and only using embryos that do not have the hereditary syndrome through the process of in-vitro fertilization (IVF).

In general, improved outcomes have been found in patients seen by surgeons who operate on the thyroid frequently. Because MTC is rare, it is also helpful for the surgeon to have familiarity with MTC specifically.

• A comprehensive neck ultrasound to include the thyroid bed and the lateral neck compartment
• Tumor markers including serum calcitonin and CEA
• Additional imaging based on extent of disease suspected
• Evaluation of vocal folds if there is concern for tumor involvement

If your entire thyroid is removed, you will be hypothyroid and will need thyroid hormone replacement in the form of daily medication.

Sometimes patients report feeling some fatigue and experience challenges with weight changes.

Testing tissue for mutation is usually reserved for when additional therapy is planned for advanced diseases.

Ideally, you would only have one operation within the neck. However, because MTC can recur, additional operations may be necessary. Knowing the diagnosis prior to surgery and performing complete preoperative imaging allows for the best chance of an optimal first surgery.

Your team can learn about the extent your disease has spread which can help with staging and determining how the disease will behave.

Not necessarily, as sometimes imaging can be used to determine if there is disease in the lymph nodes in the neck, and it is often used to determine if there is disease that has spread elsewhere in the body.

See How do I know the “Stage” of my MTC? in the Understanding the Disease section above for more information about MTC staging

In addition, diarrhea which can be problematic in MTC patients can alter the absorption of thyroid hormone into the body and require higher doses.

Vandetanib, Cabozantinib, Selpercatinib, and Pralsetinib have been approved by the Food and Drug Administration (FDA) for the treatment of MTC in the United States.

Radioactive iodine is not recommended for MTC as medullary thyroid cancer cells do not have iodine receptors and will not absorb the radioactivity and be treated by it.

At times, external beam radiation may be recommended to areas of focal progression, such as a bone metastasis or a lung metastasis that is near an airway. Rarely, if there is invasive disease in the neck involving the wall of the trachea or the esophagus, radiation may be recommended for focal treatment to prevent progression in that region in the future. However, external beam radiation therapy to the neck must be considered with significant caution and only after discussion in a multidisciplinary fashion, as radiation to the neck can lead to serious side effects, as well as limit or prevent future beneficial surgery in the neck.

Often, MTC may lead to no symptoms. If there are symptoms, the most common ones are diarrhea or facial flushing. If you develop any of the following symptoms, it may suggest recurrent disease: swallowing problems, new voice changes, or back pain.