Follow-Up Testing

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Follow-Up in the First Year and After
Understanding Your Blood Tests
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Follow-Up in the First Year and After

After your treatment, you will receive follow-up in the first year, as well as life-long monitoring.

This is for two main reasons.

• First, long-term monitoring is important to make sure that your dose of thyroid hormone replacement is appropriate— neither too low nor too high for your specific needs.
• Second, you will receive testing to find out if there is persistent disease or possible recurrence. Many people with differentiated thyroid cancer experience persistent disease or a recurrence, sometimes many years after the initial treatment. The prognosis for any person with a recurrence is better if it is discovered early. This is why life-long monitoring is important.
• The exact type of monitoring, and how often it takes place, depends on the size of the original tumor and whether the cancer had spread locally or distantly, as well as other factors.
• People free of disease receive less monitoring or testing than those with evidence of persistent disease.
• Also, testing is spread out and becomes less frequent when the patient becomes free of disease. You and your doctor should discuss a plan to fit your situation.

Monitoring will most likely include:

• Physical neck examination, including feeling the thyroid bed area. Typically, this is done every 3 to 6 months for the first 2 years, and at least once a year thereafter.
• Blood tests. Certain blood tests will determine if you are on the right dosage of thyroid hormone replacement. Your medication dose may change over time. Blood testing is also useful to monitor for cancer recurrence. The blood tests will depend on your type of thyroid cancer.
• Neck ultrasound. This test is increasingly used because it is a very sensitive way to find potential disease in the neck. It involves moving an instrument along your neck, without any pain, and there is no radiation exposure associated with it.

Also, for people in medium-risk or high-risk circumstances, long-term monitoring may sometimes include:

• RAI Whole Body Scan for people with papillary or follicular thyroid cancer, or a variant. This is generally a “stimulated” scan, with your TSH elevated. Therefore, it will be done either after thyroid hormone withdrawal (you stop taking your pills for a period of time), or after you receive Thyrogen injections. Either method will raise the level of thyroid stimulating hormone (TSH). The low-iodine diet is followed for about two weeks before this scan.
• CT Scan, particularly of the head and neck and/or the chest. If you have papillary or follicular thyroid cancer, CT testing will generally be done without contrast dye because the dye is very high in iodine. If the test reveals cancer, the use of contrast would delay potential RAI treatment until the iodine could be cleared from the body.
• MRI, particularly of the head and neck and/or the chest. The contrast dye used in an MRI is gadolinium and does not contain iodine.
• PET/CT Scan. A PET scan or combined PET/CT scan is sometimes done when blood testing in someone with differentiated thyroid cancer reveals Thyroglobulin levels above a certain measure, but the disease does not show up on an ultrasound or an RAI whole body scan.
• Chest X-ray. An X-ray may be used for low-risk patients whose initial cancer was treated via a lobectomy.

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Understanding Your Blood Tests

During the first year after your treatment, your physician may order blood tests several times to make sure you are on the right dosage of thyroid hormone replacement.

Blood testing also helps monitor for persistent or recurrent cancer.

After the first year, your doctor may order blood tests less often.

Among events that may affect your dosage of thyroid hormone replacement are weight gain or loss, pregnancy, and menopause. However, you will generally be on the same dosage for long periods of time.

Papillary and Follicular Thyroid Cancer and their Variants

There are three main blood tests:

• Thyroid Stimulating Hormone (TSH). See the section on thyroid hormone replacement therapy, linked on the left side of this page.
• Thyroglobulin (Tg): Thyroglobulin is a protein produced by thyroid cells (both normal and cancerous cells). After removal of the thyroid gland, Thyroglobulin can be used as a "cancer marker." Its number should be as low as possible. Sometimes this is termed "undetectable.” After your surgery and RAI, it may take months or years for the Tg number to come down to zero or undetectable.
  
  A positive Tg test indicates that thyroid cells, either normal or cancerous, are still present in your body. Depending on the level of Tg in your blood, your doctor may want to monitor you more closely with other tests or scans and/or prescribe additional treatment.
  
  If you did not receive RAI, your Tg level will probably be detectable. This is because some remnant thyroid tissue nearly always remains in your neck after surgery. If you had a lobectomy rather than a thyroidectomy, your remaining lobe will almost certainly produce Tg. However, it is still helpful to follow your Tg levels over time. If Tg levels increase, your doctor may recommend further imaging studies to locate the source.
  
  From time to time, your doctor may recommend what is called a “stimulated Tg” measurement. This means that your TSH is elevated, by withdrawal from thyroid hormone or by receiving injections of the drug Thyrogen, and then your Tg is measured. Thyroglobulin testing can be more accurate when your TSH level is elevated.
• Anti-thyroglobulin anti-bodies (TgAb): Some people produce anti-thyrogloblin antibodies. These are not harmful. However, they mask the reliability of the Tg value. If you have TgAb, imaging studies may be used to monitor for persistent or recurrent disease. Sometimes the antibodies disappear over time, although not always.

In addition to these tests described above, some doctors will also recommend the measurement of Free T4. If so, discuss this with your doctor.

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For more information, go to:

• Thyroid Hormone Replacement, TSH, Thyroglobulin, and Other Blood Testing
• Long Term Monitoring and Treating Recurrent or Persistent Disease