Radioiodine Ablation and Treatment for Papillary and Follicular Thyroid Cancer

(By Douglas Van Nostrand, M.D. Reprinted, with permission, from pages 201-203,231-232 of Chapters 23 and 26 of the book “Thyroid Cancer: A Guide for Patients”, (Keystone Press, 2004. Douglas Van Nostrand, M.D., Gary Bloom, and Leonard Wartofsky, M.D. See

Frequently Asked Questions

What is radioiodine ablation?
Radioiodine ablation is radiation therapy in which radioactive iodine is administered to destroy or ablate residual healthy thyroid tissue remaining after thyroidectomy.

What is radioiodine treatment?
Radioiodine treatment is radiation therapy in which radioactive iodine is administered to destroy suspected or known thyroid cancer by irradiating that tissue.

What is the difference between ablation and treatment?
Many physicians use “ablation” and “treatment” interchangeably. However, other physicians use “ablation” to mean the administration of radioiodine to eliminate any normal thyroid tissue remaining in the neck after initial surgery and “treatment” to mean the administration of radioiodine for the elimination of known or suspected metastatic disease in the neck or elsewhere.

Why do I have any thyroid tissue left after my surgery? I thought my surgeon took it all out.
Although your surgeon removed your thyroid gland, most surgeons leave behind small amounts of thyroid tissue to minimize any damage to the nerve that controls your voice box. This nerve is called the recurrent laryngeal nerve and runs behind your thyroid tissue. Your surgeon may also leave some thyroid tissue behind to make sure some of your parathyroid glands remain intact. These glands control your body’s calcium levels and are usually located within or behind your thyroid tissue.

Why do I need an initial radioiodine ablation when my physician believes he has removed all of my thyroid carcinoma?
Most physicians will recommend that patients with thyroid carcinoma undergo at least one ablation radiation therapy with radioiodine. Research and fifty years of experience suggest that the combination of surgery, radioiodine ablation, and thyroid hormone replacement can reduce the chances of your thyroid carcinoma recurring. However, there are some situations in which your physicians may not recommend an initial ablation with radioiodine.

What are the criteria for not receiving an ablation with radioiodine?
Radioiodine ablation may not be recommended depending on several factors. These include the size of the original thyroid cancer, the number of sites involved, the lack of any involvement of the borders of the thyroid or adjacent tissues, and a lack of evidence that the cancer has spread…

If radioiodine ablation is recommended, what are its goals?
Radioiodine ablation has four goals.

  • First, the ablation of any remaining normal thyroid tissue facilitates the use of the blood levels of thyroglobulin to monitor you for any progression or spread of your cancer…...
  • Second, destroying the remaining thyroid tissue will also improve the ability of the radioiodine whole body scan to monitor you for evidence of any recurrence of the cancer…
  • The third goal is to enhance the effectiveness of future radioiodine treatments, if needed, by allowing you to receive a higher dosage of radioiodine, which has the potential to deliver more radiation to your cancer cells…….
  • Finally and in select patients, ablation may reduce the chance of the thyroid cancer recurring and increase survival. However, the success of ablation achieving this objective is very controversial (see Chapter 24).

Side Effects of Radioiodine

  • Potential side effects will vary depending on the dosage of the 131I administered.
  • In regard to selecting dosages for 131I ablation or treatment, three points should be remembered. First, the type, frequency, and severity of side effects must be weighed against the benefit of the dosage for ablation or treatment. Second, although your physicians may know the potential risks and benefits of the various dosages, they cannot predict what will happen in a given patient. Everyone responds differently to 131I ablation or treatment, which often makes it difficult for a patient to decide the dosages that might be best for him or her. Your personal physician is your best resource to help you make this decision…[Some examples of potential side effects include nausea and vomiting, dry mouth, change in taste (in as many as a third of patients, typically lasting several weeks), salivary gland swelling and pain, and drop in blood counts, and others.]
  • As a general rule, side effects increase in frequency and severity with increasing dosage and frequency of administration of 131I.
  • No strict upper limit of total cumulative dosage … should be set. Many factors must be weighed including but not limited to (1) the severity of your thyroid cancer, (2) the location of the disease, (3) whether the metastasis takes up 131I , (4) whether or not you have previously responded to 131I , (5) how long ago the last treatment was administered, (6) the total blood counts, (7) what was the response of the blood counts to the last 131I treatment, (8) your age,(9) your other health problems, if any, and (10) your other options available.
  • [Regarding side effects] keep in mind three things:
    • Many of these side effects are infrequent
    • Most of the side effects are manageable.
    • The risk of the frequency and severity of the side effects must be weighed in light of the severity of your thyroid cancer.

Last updated: January 3, 2023