Treatment of Thyroid Cancer

Thyroid cancer treatment may consist of several components.  Not every case will require every component.  These components include:

1. Surgery – all thyroid cancers
2. TSH suppression with thyroid hormone replacement – some thyroid cancers
3. Radioactive iodine treatment (RAI) – some thyroid cancers
4. External beam radiation (EBR or XRT) – rarely used
5. Chemotherapy -- an emerging field
6. Regular surveillance (follow-up) – all thyroid cancers

Surgery

Almost all forms of thyroid cancer are treated primarily by surgery.  In some cases, a partial thyroidectomy is performed, but for the majority of patients a total thyroidectomy is recommended (although this is an evolving field). Occasionally the diagnosis is made after a partial surgery, and the patient undergoes completion surgery following confirmation of the diagnosis.

TSH Suppression with Thyroid Hormone Replacement

The following information pertains to those with differentiated (DTC) forms of the disease, that is, papillary or follicular.

In addition to surgery as the primary form of treatment, another vital treatment is suppression of Thyroid Stimulated Hormone (TSH).  The TSH is a hormone produced by the pituitary gland. The TSH ‘calls for’ T4 and T3 hormones to be made by and released from the thyroid gland. TSH also plays a role in the growth of thyroid cells.  To help you understand the process, imagine that the thyroid gland - or its substitute by pill - is the body’s furnace, and the pituitary gland is the thermostat. If need be, the thermostat calls for ‘more heat’ by sending a TSH signal, and the furnace responds by sending T4 and T3 throughout the body. Like other thermostats, there is a feedback system (a loop) such that the pituitary can sense the levels of thyroid hormone in the body and increase or decrease production of TSH to direct the thyroid’s production in order to maintain an appropriate level of T4 and T3 in the body.

Source: www.endocrineweb.com/tests.html

In healthy persons with normally functioning thyroid glands, the TSH is expected to be in the range of 0.4 to 5.0 mIU/L (µIU/mL). However, it is common for thyroid cancer patients to take a daily dose of levothyroxine (T4) that is high enough to cause the measure of the TSH to be very low or suppressed.  Suppressive therapy means that thyroid cancer patients’ TSH is intentionally kept in the range of 0.01 to 3.0.  The treating doctor will target the TSH (measured by blood tests) within a range that is ideal for the patient based on general risk factors. A balanced approach must be taken as very low TSH increases the chance of bone loss and heart arrhythmia, whereas high TSH is associated with increases in the chance of recurrence of the disease.

Radioactive Iodine Treatment (RAI)

Radioactive Iodine treatment (RAI) is a unique form of treatment for the differentiated forms of thyroid cancer (papillary & follicular).  For full details of this form of treatment, click here.

External Beam Radiation (EBR or XRT)

This treatment is not commonly used for thyroid cancer but may be required in special circumstances.  This decision would be made by your thyroid cancer specialist and would be administered by a radiation oncologist, usually in a specialized centre. 

Chemotherapy

For some patients with metastatic differentiated thyroid carcinoma (DTC) that progresses despite RAI treatment and TSH suppression, targeted chemotherapies are emerging as effective alternatives for progressive disease, although most remain investigational. New chemotherapies are also being utilized with some patients with anaplastic and medullary disease. To read more about these click here.

Regular Surveillance (Follow-up)

This is a critical component of the treatment of thyroid cancer.  Regular surveillance consists of blood tests, regular check-ups by the doctor (feeling the neck) and may include some imaging tests like ultrasounds or whole body scans. 

As well as monitoring TSH levels, follow-up blood tests measure thyroglobulin (Tg). Tg is a unique protein which is created only by normal and differentiated cancerous thyroid cells.  Thus, a patient who had a total thyroidectomy surgery would be expected to have a very low or undetectable Tg measurement. Because only thyroid cells create the Tg protein, this protein acts as a ‘cancer marker’ for remnant or recurrence of the disease. Sometimes a treatment of Radioactive Iodine (RAI) is needed to achieve the effect of low or undetectable Tg. In very rare cases more than one treatment is necessary or other treatment modalities are necessary such as the use of external beam radiation (EBR or XRT). The Tg level in the blood should be tested regularly to look for recurrence of the disease.  Whenever a Tg level is ordered, the anti-thyroglobulin antibodies must also be tested at the same time.  A Tg blood test can be taken at any time.

Occasionally, as part of routine follow-up, a Tg blood test may be ordered while the patient is L-T4 withdrawn (patient is hypothyroid) or TSH-stimulated (patient is on Thyrogen®).  High TSH levels will stimulate thyroid cells (and differentiated thyroid cancer cells) to make Tg.  Therefore, if the TSH level is purposely increased AND the Tg level remains low or undetectable, then (in most cases) one can be reassured that there is no recurrence of disease.  As in the case of RAI treatment, the stimulation can be done either by “going hypo” or with Thyrogen®. 

At the time of stimulation, a whole body scan (WBS) may or may not be included in the testing to mark the progression or elimination of the disease.  The WBS requires that a test-dose (or scanning dose) of radioactive iodine be given, in the range of 4-8 mCi. 

If Thyrogen® is being used and where a test-dose (scanning dose) of RAI is given, patients are typically given two doses of Thyrogen® by injection; the first on a Monday and the second on Tuesday, having their test-dose RAI on Wednesday and Thyroglobulin (Tg) blood test and Whole Body Scan (WBS) on Friday. Some doctors prefer to repeat the Tg blood test twice (Wednesday and Friday) to ensure the test was properly conducted at least once by the laboratory. If no WBS is included, the schedule for the Thyrogen® is the same.

For detailed product information about Thyrogen® including side effects and reactions, contra-indications, special information regarding the dosage (such as those for pregnant women or children), click here.

Thyrogen® Schedule

(For both Tg Testing and WBS)

 

Monday	Tuesday	Wednesday	Thursday	Friday
Thyrogen® Injection #1	Thyrogen® Injection #2 (optimally same time of day as Monday’s injection)	Swallow RAI capsule or liquid  (given by Nuclear Medicine dept) ONLY if ordered by the doctor	Off	1. Have a blood test for Tg and anti-TgAb   2. Have a Whole Body Scan (Nuclear Medicine dept).

 

PET-CT Scans

Occasionally PET-CT scans are utilized to image possible recurences. This type of scan (which usually uses a glucose contrast known as FDG) is most often used with patients who have a Tg of at least 10. The reason for this is that thyroid tissue has a tendency towards becoming less iodine-avid as it becomes more aggressive (de-differentiated). At the same time, it often becomes more glucose/sugar-avid.

The use of PET-CT for thyroid cancer patients is an evolving field, and new contrast materials are also being used in select cases or circumstances.  For a full description see:

Update of PET-CT for Thyroid Cancer

Two images on left are from a WBS (using RAI).  Image on right from a PET-CT scan using FDG. PET scan shows more information about metastases in same patient. Ref: as above link.

 

Last Word

The need and frequency of stimulated Tg, WBS and/or other testing will be determined by the doctor based on a number of factors.  However, one of the most important things to remember is that regular surveillance (follow-up) is an absolutely critical component of thyroid cancer treatment.