Follicular Thyroid Cancer Long-Term Follow-Up: Why Do I Need It?
You may have heard or experienced one of the following:
- You have the "good thyroid cancer".
- You didn't know you had follicular thyroid cancer until after your thyroid surgery.
- Your follicular thyroid cancer was not completely removed (this is called persistent follicular thyroid cancer).
- Your follicular thyroid cancer has come back! (this is called recurrent follicular thyroid cancer).
- Your follicular thyroid cancer is located in other sites of your body other than your neck (this is distant spread of your cancer or distant metastases)
- You had a follicular thyroid cancer and you underwent removal of half of your thyroid gland -called a thyroid lobectomy.
- You had a follicular thyroid cancer and underwent removal of all of your thyroid gland.
- Your blood marker for your follicular thyroid cancer (called thyroglobulin) is elevated.
- To make sure that your thyroid hormone levels in your blood are at the right level for you! It is possible you may not require any thyroid hormone pill or supplement, however most follicular thyroid cancer patients during follow-up are maintained on thyroid hormone pills. There are several different types of thyroid hormone pills and you should discuss this with your endocrinologist to make sure that you are feeling well and your hormone levels are right for you. Your thyroid hormone should not be too low or too high for your specific needs. The amount of thyroid hormone that you may need may change throughout your lifetime due to many reasons including age, body weight, pregnancy, and more.
- To determine whether all of your follicular thyroid cancer was completely removed. If follicular thyroid cancer is still evident in your neck following your initial surgery, this is called persistent follicular thyroid cancer. Unfortunately, this is more common than we would like to recognize. Persistent follicular thyroid cancer occurs in nearly 11% of patients with the earliest forms of follicular thyroid cancer. Persistent follicular thyroid cancer is largely preventable in almost all patients. After the initial follicular thyroid cancer surgery, determining whether there is persistent cancer can be difficult because of all the changes associated with the surgery and healing process. Don't worry and don't be in a hurry! But don't make the same decisions that lead you to this issue. Make sure your next evaluation and surgery is performed by a thyroid cancer team that is truly expert in evaluating and managing follicular thyroid cancer. We have written a complete section on persistent follicular thyroid cancer just for you so you can understand this issue and how best to approach it.
- To determine whether your follicular thyroid cancer has come back. If your follicular thyroid cancer has been gone for a period of time and comes back, this is called recurrent follicular thyroid cancer. Important questions that need to be asked:
- How old are you?
- What does the follicular thyroid cancer look like under the microscope?
- Where has the recurrent follicular thyroid cancer found?
- What treatment (s) have you had for your follicular thyroid cancer?
Follicular Thyroid Cancer Follow-Up: Factors Influencing How Often and What Studies Should Be Obtained
Follicular thyroid cancer patients, who have completed treatments, the timing of follow-up appointments and the types of studies obtained in the follow up of their follicular thyroid cancer depends upon:
- 1) The age of the follicular thyroid patient-when they were diagnosed.
- 2) The follicular thyroid cancer treatment(s) the patient received.
- 3) The locations the follicular thyroid cancer was found in the body.
- a. Thyroid gland only
- b. Thyroid gland and neck lymph nodes only
- c. Sites outside of the neck (distant spread of the follicular thyroid cancer).
- 4) Whether the follicular thyroid cancer patient was ever considered free of disease.
- 5) The follicular thyroid cancer pathology (What was found in the follicular thyroid cancer surgery specimen)? We have written a whole section on this for you to better understand your follicular thyroid cancer. This is called Pathology Follicular Thyroid Cancer Staging (TNM staging)
- a. How big was the follicular thyroid cancer within the thyroid gland?
- b. What did the follicular thyroid cancer cells look like under the microscope?
- c. Did the follicular thyroid cancer grow out of the confines of the thyroid gland itself?
- i. If it did grow out, what did it grow into?
- 1. The muscle which lays over the thyroid gland?
- 2. The breathing tube (trachea)
- 3. The swallowing tube (esophagus)
- d. Did the follicular thyroid cancer grow into blood vessels or lymphatic vessels?
- e. Did the follicular thyroid cancer grow into nerves or other nearby structures?
- f. Did the follicular thyroid cancer spread into neck lymph nodes?
- i. The lymph nodes along the breathing tube or swallowing tube- called the central compartment lymph nodes?
- ii. The lymph nodes on the side of the neck- called the lateral neck?
- g. Did the follicular thyroid cancer spread to other areas of the body outside of the neck? Meaning is there distant spread of the cancer?
- i. Lungs
- ii. Bone
- iii. Liver
- iv. Other sites
Follicular Thyroid Cancer Follow-Up: How Frequent and What Studies Should Be Obtained
Follow-up of follicular thyroid cancer patients is usually accomplished by an endocrinologist every six months for the first year and then annually thereafter if there is no evidence of disease.
- Physical examination: This will include examination of the neck and thyroid bed and examination of the voice box if there is concern over changes in voice or swallowing
- Ultrasound of the neck (see ultrasound of the neck for follicular thyroid cancer)
- Blood tests for :
- 1) Free T4 level: This is the blood level of the major hormone normally produced by the thyroid gland. It is also a direct measurement of the most commonly prescribed thyroid hormone pill, levothyroxine. The dose of thyroid hormone pill will be based upon the blood thyroid stimulating hormone (TSH) level described below.
- 2) TSH (Thyroid Stimulating Hormone): The potential risk of your follicular thyroid cancer recurring determines the amount of thyroid hormone that will be prescribed to you in the replacement of your thyroid hormone. The American Thyroid Association has guidelines for the blood level of TSH which should be sought based upon the risk of the follicular thyroid cancer recurring. That risk may be low, intermediate or high risk and each is associated with a different range of TSH blood levels.
- In low-risk patients, the 2015 American Thyroid Association Guidelines recommend that the goal for initial TSH level usually be 0.5 to 2.0 mU/L, which is within the normal range. For some patients, the goal is 0.1 to 0.5 mU/L, which is just below or near the low end of the normal range.
- In intermediate-risk patients, the initial TSH goal is 0.1 to 0.5 mU/L. This goal may change to a normal range of TSH following long term follow-up and no detectable thyroglobulin.
- For high-risk patients, the thyroid hormone dose will be high enough to suppress the thyroid stimulating hormone (TSH) below the range that is normal for someone not diagnosed with follicular thyroid cancer. The goal is to prevent the growth of follicular thyroid cancer cells while providing essential thyroid hormone to the body. At first, TSH levels will probably be suppressed to below 0.1 mU/L. The level may later change to 0.1 to 0.5, depending on your body's response to the treatment and time.
- 3) Thyroglobulin: Thyroglobulin is a protein produced by thyroid cells (both follicular thyroid cancer and normal 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 with or without radioactive iodine, it may take months or even years for the thyroglobulin number to come down to zero or undetectable.
A detectable thyroglobulin test indicates that either follicular thyroid cancer cells or normal thyroid cells are still present in your body. Depending on the level of thyroglobulin in your blood, your doctor may want to monitor you more closely with other tests or scans and/or prescribe additional treatment.
If you had a thyroid lobectomy rather than a total thyroidectomy, your remaining thyroid lobe will almost always produce some amount of Thyroglobulin. However, it is still helpful to follow your Thyroglobulin levels over time. If significant changes in Thyroglobulin levels occur over time, your doctor may recommend further imaging studies to locate the source.
Not all follicular thyroid cancer produce thyroglobulin. In particular, as the cells sometimes begin looking more angry under the microscope (called dedifferentiation or becoming poorly differentiated), they may lose the ability to produce thyroglobulin. Most follicular thyroid cancers, however aggressive they may become, usually produce thyroglobulin and allow this blood measurement to be an effective means of monitoring their cancer.
From time to time, your doctor may recommend what is called a "stimulated Thyroglobulin" measurement. This means that your TSH is elevated, by withdrawal from thyroid hormone or by receiving injections of the drug called Thyrogen, and then your Thyroglobulin is measured. Thyroglobulin testing can be more accurate when your TSH level is elevated.
- 4) Thyroglobulin antibody: Some people produce a very large protein that for some reason recognizes the normal thyroglobulin protein as being "abnormal". These very large proteins are called anti-thyroglobulin antibodies. These are not harmful but are a sign of an autoimmune disease where the body recognizes itself as being abnormal. The presence of Thyroglobulin antibodies makes Thyroglobulin a largely useless blood test for monitoring follicular thyroid cancer. Sometimes the Thyroglobulin antibodies may disappear over time following surgery for follicular thyroid cancer. Although that does not commonly occur even in follicular thyroid cancer patients which are cured.
Follicular thyroid cancer patients with medium risk or high risk of their cancer recurring may require additional studies including:
- 1) Radioactive Iodine Whole Body Scanning: This is generally performed with elevated blood levels of TSH. Elevated TSH levels can be obtained by withholding thyroid hormone and making the patient hypothyroid or by giving the patient TSH injections called Thyrogen. Both methods of raising TSH levels are equal in delivering radioactive iodine. A low iodine diet is required for at least two weeks before this examination.
- 2) CT scanning of the neck and or chest: CT scanning of the neck is obtained for follicular thyroid cancer patients when there have been surgical or pathology findings of the follicular thyroid cancer which suggest a high risk of recurrence in locations that ultrasound has limitations. This includes the voice box (larynx), trachea (breathing tube) and esophagus as well as deeper structures in the neck and below the collar bones or chest wall. CT scan of the neck should be obtained with contrast otherwise its use is extremely limited.
In follicular thyroid cancer patients with extensive angioinvasion (blood vessel invasion) or soft tissue extension or the rare event of a history of spread to neck lymph nodes, above 50 years of age, a baseline CT scan of the chest should routinely be obtained and periodically re-examined approximately once annually. The baseline CT scan can be used in comparison if Thyroglobulin levels are shown to be increasing during the period of follow-up or recurrence is ever discovered.
- 3) PET/CT scanning: A PET scan is a special imaging study using a specially designed sugar that "lights up" on nuclear imaging and when combined with a CT scan is called a PET/CT scan. follicular thyroid cancer follow-up may include this scan when there is:
- 1) an "angry appearing" follicular thyroid cancer
- 2) distant spread in the body of the follicular thyroid cancer
- 3) neck recurrence of the follicular thyroid cancer
- 4) significant elevation of thyroglobulin levels above what would be anticipated for the known disease
- 5) when there is known recurrent cancer but no detectable thyroglobulin.
- 4) MRI scanning: MRI scanning is particularly beneficial for examination of the brain and spinal column when there has been a history or concern for involvement of follicular thyroid cancer in those sites. This study does not produce any radiation effect and is given with an intravenous contrast agent called gadolinium. There is no iodine present in gadolinium and therefore it does not conflict with radioactive iodine scanning.