You need regular checkups after treatment for thyroid cancer. Even when there are no longer any signs of cancer, the disease sometimes returns because cancer cells remained somewhere in the body after treatment.
Your doctor monitors your recovery and checks for return of the cancer with blood tests and imaging tests. If thyroid cancer returns, it is most commonly found in the neck, lungs, or bones.
Also, checkups help detect health problems that can result from cancer treatment. People treated with radioactive iodine therapy or external radiation therapy have an increased chance of developing other cancers later on. If you have any health problems between checkups, you should contact your doctor.
People treated for papillary or follicular thyroid cancer have blood tests to check the levels of TSH and thyroglobulin. Thyroid hormone is normally stored in the thyroid as thyroglobulin. If the whole thyroid has been removed, there should be very little or no thyroglobulin in the blood. A high level of thyroglobulin may mean that thyroid cancer has returned. Your doctor helps you get ready for a thyroglobulin test in one of two ways:
- You stop taking your thyroid hormone pills for a short time: About six weeks before the thyroglobulin test, your doctor may change the type of thyroid hormone pill you take. About two weeks before the test, you stop taking any type of thyroid hormone pill. This can cause uncomfortable side effects. You may gain weight and feel very tired. It may be helpful to talk with your doctor or nurse about ways to cope with such problems. After the thyroglobulin test, you can take your usual thyroid hormone pill again.
- You get a shot of TSH: Your doctor may give you a shot of TSH. If any cancer cells remain in the body after treatment, TSH causes them to release thyroglobulin. The lab checks the level of thyroglobulin in the blood. People who get this shot don't have to stop taking their thyroid hormone pill.
People treated for medullary thyroid cancer have blood tests to check the level of calcitonin and other substances.
In addition to blood tests, checkups may include one or more of the following imaging tests:
- Ultrasound: An ultrasound exam of the neck may show whether cancer has returned there.
- Whole body scan: To get ready for the whole body scan, you either stop taking your thyroid hormone pill for several weeks or you get a shot of TSH (as described above for the thyroglobulin test). Most people need to avoid eating shellfish and iodized salt for a week or two before the scan. Your doctor gives you a very small dose of radioactive iodine or another radioactive substance. The radioactive substance is taken up by cancer cells (if any cancer cells are present). Cancer cells show up on the scan.
- PET scan: Your doctor uses a PET scan to find cancer that has returned. You receive an injection of a small amount of radioactive sugar. A machine makes computerized pictures of the sugar being used by cells in the body. Cancer cells use sugar faster than normal cells, and areas with cancer look brighter on the pictures.
- CT scan: A CT scan may show whether cancer has returned.
- MRI: MRI may show whether cancer has returned.