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Radioactive Iodine for Papillary Thyroid Cancer

A Safe and Effective Second Line of Treatment

If your papillary thyroid cancer (also known as papillary thyroid carcinoma) did not spread, and if your tumors were small, a thyroidectomy is often enough to remove the cancer from your body. But larger tumors and those that have spread (metastasized) to the lymph nodes and other parts of the body require additional treatment. This treatment is radioactive iodine therapy.

Though radioactive iodine therapy is commonly used as a follow-up treatment for larger, more aggressive tumors, it can also be used as a safeguard treatment for smaller tumors if there are worrisome features associated with the cancer, including an aggressive type, blood vessel (vascular) invasion, or multi-focal cancer.

Radioactive iodine therapy, which your doctor may refer to as radioactive iodine ablation, is used about 1 to 2 months after you have papillary thyroid cancer surgery. The goal of this treatment is to kill any cancer cells that may remain after surgery.

Preparing Your Body for Radioactive Iodine Treatment
Radioactive iodine is a safe therapy because the radioactive iodine is primarily absorbed by thyroid cells. Thyroid cells are the main cells in the body that can absorb iodine, so no other cells are exposed to the radiation. When the thyroid cells—both healthy and cancerous—absorb the radioactive iodine, they are damaged or destroyed.

Thyroid cancer cells, however, don't take up the radioactive iodine as easily as the healthy thyroid cells do. To encourage the cancerous cells to absorb the radioactive iodine, your doctor may suggest one or both of these methods:

  • Increase your levels of thyroid stimulating hormone (TSH). Healthy thyroid cells use iodine to make thyroid hormones, but cancerous thyroid cells absorb only a very small amount of iodine. What high levels of TSH do is stimulate the cancerous thyroid cells to absorb more iodine. That way, the cancerous cells will be more eager to absorb the radioactive iodine.

    So how are your TSH levels raised? There are 2 ways. The first involves stopping thyroid hormone replacement therapy.

    After thyroid surgery, you may need to take thyroid hormone replacement therapy to compensate for the lack of T4 and T3 thyroid hormones being produced naturally. But to raise TSH levels, you need to stop taking T4 hormone replacement therapy before radioactive iodine therapy is set to begin (it's usually about 5 weeks before). This decrease in thyroid hormones triggers the pituitary gland to release more TSH.

    Higher TSH levels will make you temporarily hypothyroid. To reduce hypothyroidism symptoms, you may take T3 hormone replacement therapy until about 2 weeks before you receive radioactive iodine therapy. You may resume thyroid hormone replacement therapy within 2 days after radioactive iodine treatment.

    Another way to raise your TSH levels is by taking 2 doses of 

    Thyrogen® (thyrotropin alfa for injection). This FDA-approved drug is specifically used to raise TSH levels before radioactive iodine treatment.

  • Reduce iodine levels in your body with a low-iodine diet. After being deprived of iodine from your diet, all thyroid cells will be more likely to absorb the radioactive iodine. Starting a low-iodine diet 2 weeks before radioactive iodine treatment is enough time to deplete your body's iodine levels and prepare it for radioactive iodine therapy. For low-iodine recipes, visit the Thyroid Cancer Survivors' Association Low-Iodine Cookbook.

Receiving Radioactive Iodine Treatment
After preparing your body for radioactive iodine therapy, your doctor will give you a very small amount of iodine to see if there are any pieces of thyroid remaining. After one day, your doctor will scan your neck with a special camera. If the scan shows that the iodine was absorbed in your neck, that means there are remnants of your thyroid left. In the great majority of cases—95%, in fact—there are thyroid remnants that remain after thyroid surgery.1

A pretherapy scan may or may not be obtained before the actual radioactive iodine treatment. If this is done, your doctor will give you a small dose of radioactive iodine (the exact dose will be determined by your doctor) and a scan will be obtained to see how much residual tissue you have in the neck and if there is spread outside the thyroid. Based on these findings, then your doctor will administer, within 72 hours of the initial prescan, the radioactive iodine does to you. This will destroy remaining thyroid remnants in the neck, in addition to any other possible thyroid cancer cells that have metastasized. Then a post-therapy scan is obtained 10 days later to evaluate the uptake in the body.

You won't need to be hospitalized when you receive radioactive iodine because it's taken as an oral pill. One dose is usually enough to kill the remaining thyroid fragments and cancer cells. Radioactive iodine therapy can take anywhere from a few weeks to a few months to fully eliminate all papillary thyroid cancer cells.

Special Considerations after Treatment
When you return home after receiving radioactive iodine, you need to take into account a number of precautions to prevent radiation exposure to others. Below is a list of general guidelines. Keep in mind that your doctor's specific instructions always take precedence.

  • You should sleep alone for the first 3 to 5 nights after treatment.
  • Avoid personal contact for about 3 to 7 days after treatment. In those first 3 days after therapy, you should stay a safe distance away from others (6 feet away, approximately). It's a good idea to avoid public places.
  • For the first 3 days after receiving radioactive iodine, don't share anything—this includes utensils, bedding, and personal items. You'll even have to do your laundry and dishwashing apart from the rest of your family. Shower daily and wash your hands often. If you can designate a bathroom in your house for only your own use, then do so. But if not, wipe the toilet seat after each use.
  • Drink plenty of water. This will stimulate the removal of radioactive iodine through your urine.

If you have any questions about having radioactive iodine as part of your papillary thyroid carcinoma treatment plan, don't hesitate to talk to your doctor. He or she will walk you through how this therapy safely and effectively treats your papillary thyroid cancer.

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