Radioactive Iodine Treatment (RAI)

Radioactive Iodine treatment (RAI) is a unique form of treatment for the differentiated forms of thyroid cancer (papillary & follicular). It is not often used in patients who are at low risk for recurrence.  Generally speaking, low risk patients are those who had a singular cancerous nodule without 'aggressive features', are less than 45 years old, and have no family history of thyroid cancer. These patients may be defined as having Stage I thyroid cancer.

For a full explanation of the ‘staging’ for thyroid cancer see the American Thyroid Association’s Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer (Table 4)

For those who are at higher risk of recurrence, the option is available and may be recommended by the treating physician.

The following information applies to those who have been advised to have RAI treatment by their doctor.

RAI treatment has two primary purposes: 

• The treatment destroys any remaining thyroid cells (both normal and cancerous) and minimizes the risk of recurrence.  This is also known as ablation therapy.
• Destroying any remaining normal or cancerous thyroid tissue left behind after the thyroidectomy surgery facilitates the use of a unique protein marker called Thyroglobulin (Tg) in the future. Tg is measured in blood tests.

A treatment dose of RAI is usually in the range of 3.7-5.5 GBq (100 or 150mCi), but can vary based on the size or number of initial tumours, aggressive features of the pathology, and other risk factors. The RAI treatment may be given anytime, but is usually used sometime within six weeks to six months post-surgery.

Some specialists reverse the protocol. That is, they closely follow patients in the post-surgery months using ultrasound and blood tests (such as measuring Tg) and keep the radioactive iodine treatment an option if the test results indicate its necessity.

Approximately one week after having the RAI treatment, a nuclear scan known as a Whole Body Scan (WBS) is normally given.  The scan will indicate how much remnant tissue remains in the neck area following the surgery, and may indicate any metastases (spread) of the cancer to other parts of the body.

One of the ways to maximize the uptake of the radioactive iodine is by stimulating the thyroid cells to take up the radioactive iodine by raising the TSH level.  There are 2 ways of achieving a high TSH level.  They include “going hypo” or using Thyrogen®, a medication given by injection (see section below). Another part of the preparation is to go on a Low Iodine Diet.

The following is a list of suggested items for patients to take to the hospital with them, if they will have a period of time in a hospital isolation room, following their RAI treatment (inquire if you will have hospital isolation or home-based isolation):

 

RAI Isolation Room Essentials

 

 

 

The following resources are provided for those with questions about how to prepare themselves for precautions that should be taken in the days following, once RAI treatment has been given.

RAI precautions, by Ian Adam

RAI precautions, from the ATA

RAI precautions, from Amdur, Snyder and Mazzaferri

 

"Going Hypo"

Our bodies require thyroid hormone (T4); a hormone taken in synthetic form (by a daily pill) once the thyroid has been removed.  The body also requires T3 which it converts from T4. Without thyroid hormone, the body produces an increasing amount of thyroid stimulating hormone (TSH).  An elevated TSH of at least 30 mIU/L is needed for the RAI treatment to be effective. To achieve this rise in TSH, patients may be instructed to stop taking their thyroid hormone replacement pills.

Becoming hypothyroid by hormone withdrawal, involves stopping levothyroxine (L-T4; the drug’s brand names in Canada are Synthroid and Eltroxin) for approximately 4-6 weeks prior to RAI treatment.  During the time that levothyroxine is not taken, Cytomel (L-T3) may be prescribed. Cytomel is a fast-acting (and fast dissipating) form of thyroid hormone used to minimize the symptoms of hypothyroidism during hormone withdrawal. Cytomel is stopped approximately 2 weeks prior to RAI treatment.

‘Going hypo’ is a gradual process with symptoms (if any) increasing slowly over the six week period. The longer the patient is off of thyroid hormone, especially during the last two weeks prior to RAI treatment when no thyroid hormone is taken, the more likely the patient will experience symptoms of hypothyroidism.

Some Symptoms Associated with Hypothyroidism:

• Tiredness, loss of energy, weakness
• Trouble sleeping, nightmares or excess sleep
• Puffiness especially in the face and bloating
• Loss of ability to concentrate, memory loss, absentmindedness
• Weight gain
• Anxiety, panic attacks, irritability, mood swings
• Depression
• Dry eyes, skin and hair; hair loss
• Change in menstrual cycle
• Joint pains and stiffness, muscle cramps
• Intolerance to cold
• Constipation and/or nausea
• Tingling or numbness in fingers or toes
• Itchiness
• Ringing in ears
• Slight changes in eyesight

 

Thyrogen®

As an alternative to a patient ‘going hypo’, doctors have the option of effectively raising the TSH level by giving the patient TSH in the form of Thyrogen® (rhTSH) to prepare patients for RAI treatment. In that case, the patient does not withdraw from their thyroid hormone but continues taking their daily dose of L-T4 each day.  They do not become ‘hypo’ or have associated symptoms. This form of preparation for RAI treatment is known as ‘TSH stimulated’. When taking Thyrogen® in preparation for RAI treatment it is not necessary to have a measured TSH of at least 30 mIU/L as it is during the hypo or ‘withdrawal preparation’.

Thyrogen® is fast-acting and fast-dissipating and requires two visits to a doctor (or other clinician) as it is given by injections.  Most patients have mild (if any) side effects from Thyrogen® and are delighted to avoid ‘going hypo’ as described above. If Thyrogen® is selected, patients will need to get the injections on the 2 days just prior to the RAI treatment. 

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.

To view the typical schedule for injections of Thyrogen®, click here.

In some Canadian provinces, the cost of Thyrogen® is not covered by the provincial medical/drug programs, nor by local hospital formulary programs. In other provinces, the cost of Thyrogen® is covered. Where the costs are not covered, patients must pay for it themselves or apply to their private health insurance for full or partial coverage. 

Some provinces also have drug programs available which are related to income level needs. The current cost for the two injections of Thyrogen® that come within one kit, is approximately $1,600.  

Patients should be aware that the Thyrogen® kit does not include sterile water, which is a necessary component of the injection. Patients should be sure to pick up sterile water at the pharmacy with their prescription of Thyrogen®. Pharmacies charge up to $10 for the water.

Click here to view information about provincial coverage of the costs of Thyrogen® (note: enter drug “Thyrogen” and DIN # 02246016)

Note:

A study by Tuttle et al, indicates that use of Thyrogen® to prepare for RAI treatment is more effective in ablating thyroid tissue, than is hypo preparation (hormone withdrawal prep). They caution that their study was completed with patients with "small volume metastases". To view study summary click here.

 

Low Iodine Diet

To ensure that absorption of the radioactive iodine is maximized, patients should reduce the dietary intake of iodine prior to the use of RAI.  This can be achieved through a Low Iodine Diet (LID).  To view information about the Low Iodine Diet, click here.