To Use or Not to Use 131I in Thyroid Cancer.

Purpose: The purpose of the following commentary is to discuss recent controversies in the use of radioactive iodine for differentiated thyroid cancer (DTC).

Methods: R. M. Tuttle (Thyroid 2010; 20:257-263), at Memorial Sloan Kettering Cancer Center, has enumerated the well-accepted goals of radioactive iodine therapy (RAIT) in DTC: (1) ablate residual thyroid to facilitate future surveillance, (2) "adjuvant therapy" for residual radioactive iodine-avid disease, and (3) a post-RAIT scan may reveal unknown local and/or distant metastases. Using these goals as a guide, the authors have critically reviewed a recent movement to decrease the use of RAIT in DTC that is being advocated by some investigators.

Results: As a result, a recent article has highlighted this new treatment philosophy. A 2017 publication in the Journal of Clinical Oncology (Molenaar et al, 2017 0:JCO.2017.75.0232) recommends that RAIT not be used in low- or intermediate-risk DTC. In this article, the authors claim that the RAIT risks in DTC, particularly leukemia, outweigh its potential benefits. This change, if adopted, in our opinion will have profound deleterious consequences on patient outcomes. We also have identified a major problem with the article of Molenaar et al. The authors use the American Thyroid Association's criteria for staging thyroid cancer. In our opinion, this method of staging is severely flawed. We also quantitatively compare the article's alleged risk of RAIT-induced leukemia with the benefits of RAIT for DTC.

Conclusions: In summary, this matter must be debated before eliminating RAIT in low- or intermediate-risk DTC. If RAIT is eliminated for these patients, many such patients will no longer benefit from the RAIT goals listed by R. M. Tuttle, including the critical advantage of potentially improved overall and event-free survival.