Radioactive Iodine for Thyroid Cancer

This is a detailed section on the use of radioactive iodine for thyroid cancer

Radioactive iodine is one of the many steps in treating thyroid cancer also called thyroid ablation or thyroid cancer treatment. Radioactive iodine ablation (RAI) is indicated when treating differentiated thyroid cancer that has spread beyond the thyroid. Thyroid cancer can be staged with the AJCC/UICC or with the NTCTCSG system which can predict disease mortality and help to plan for possible radioactive iodine. 

In differentiated thyroid cancer, several classification and staging systems are available (See below)all of which reliably predict disease-specific mortality. However, they usually are not designed to adequately predict recurrence for individual patients. In addition, the estimates of the risk of recurrence and death usually do change over time depending upon how well the patient responds to initial therapy.

The risk of recurrence, however, follows a continuum across the three discrete risk categories (low, intermediate, and high). (See below)

Initial risk assessments are actively modified based on data obtained during follow-up that reflect the individualized patient's response to therapy. This dynamic risk assessment approach allows for more accurate risk assessments than either a static estimate of risk based on the TNM staging system or the ATA risk of recurrence classification system.

It should be recognized that no staging system predicts outcome in individual patients with 100 percent accuracy; as a result, clinicians should use individual clinicopathologic characteristics to determine the specific treatment for a given patient.

Following a low iodine diet during the 2-3 week period prior to radioactive iodine therapy will make the treatment more effective. This treatment uses radioactive iodine (131I) to destroy leftover microscopic thyroid cancer cells as well as any normal thyroid tissue that might remain after surgery. Destroying these cells makes it easier for doctors to follow patients for signs of thyroid cancer recurrence. Radioactive iodine treatment is used in most patients with differentiated papillary, follicular and Hurthle cell thyroid cancers. There are specific precautions to take after radioactive iodine is given. There are common side effects of radioactive iodine.

Guidelines from 2015 American Thyroid Association and updates from AJCC 2017
TNM staging

* The DSS is the Disease Specific Survival- defined as the percentage of people in a study or treatment group who have not died from a specific disease in a defined period of time. The time period usually begins at the time of diagnosis or at the start of treatment and ends at the time of death. Patients who died from causes other than the disease being studied are not counted in this measurement.



TSH goals while under treatment

Andrey Bychkov, M.D., Ph.D. 7 August 2018, last major update December 2017 
THYROID Volume 26, Number 1, 2016 ª American Thyroid Association
Hay ID, Hutchinson ME, Gonzalez-Losada T, McIver B, Reinalda ME, Grant CS, Thompson GB, Sebo TJ, Goellner JR 2009 Papillary thyroid microcarcinoma: a study of 900 cases observed in a 60-year period. Surgery144:980–987
Ross DS, Litofsky D, Ain KB, Brierley JD, Cooper DS, Haugen BR, Jonklaas J, Ladenson PW, Magner J, Robbins J, Skarulis MC, Steward DL, Maxon HR, Sherman SI 2009 Recurrence after treatment of micropapillary thyroid cancer. Thyroid 19:1043–1048.
van Heerden JA, Hay ID, Goellner JR, Salomao D, Ebersold JR, Bergstralh EJ, Grant CS 1992 Follicular thyroid carcinoma with capsular invasion alone: a nonthreatening malignancy. Surgery. 112:1130–6.
Sherman SI et al. Prospective multi center study of thyroid carcinoma treatment: initial alaysis of staging and outcome
Butler et al. Thyroid Vol 20, pp 1423 - 1424 Nov 12 2010