Response to Tulchinsky and Avram re: “Long-Term Outcomes of Patients with Papillary Thyroid Cancer Undergoing Remnant Ablation with 30 Millicurie Radioiodine”

Dear Editor:

Tulchinsky and Avram raise several issues with regards to our study (1,2). In an era of individualized medical care, patient management is incumbent upon risk stratification and patient selection. Historically, risk stratification was formulated by a composite of clinical profiling, surgical findings, pathology interpretation, postoperative neck sonography, stimulated thyroglobulin levels, and, when available, a pre-ablation diagnostic ¹³¹I whole-body scan. At our institution, radioiodine for purposes of ablation is given in an outpatient setting in low doses (i.e., 30 mCi) to patients believed to be structurally disease free after total thyroidectomy, as judged by the treating endocrinologist. This paradigm excluded all very low-risk (i.e., papillary thyroid microcarcinomas), many low-risk, most intermediate-risk, and all high-risk patients. These groups of individuals either were not ablated or were given high therapeutic doses of radioiodine. Indeed, this was a selection process based on a composite of all the aforementioned variables and pivoted by the endocrinologist. Our goal was to report on the long-term outcomes of only those patients who were considered by the principal investigator as appropriate, although not always optimal, for low-dose ablation. Indeed, the impact on prognosis of microscopic extrathyroidal extension without soft tissue invasion, minimal vascular invasion, multifocality, and microscopic lymph node metastasis was uncertain in the early years and the response to low activity radioiodine was explored in this study. In addition, we wished to compare our findings with those of other international groups that reported their results with similar groups of patients. In properly selected patients, if low-dose radioiodine is used, one can expect favorable clinical outcomes, whether they are prepared by thyroid hormone withdrawal or recombinant human thyrotropin. Indeed, one need only review table 2 to learn that at the end of the last follow-up, 14 patients of the entire cohort had persistent disease (4.6% of the low-risk group and 3.0% of the intermediate-risk group had persistent disease). The low rate of persistent disease in the latter group is probably a reflection of this patient selection for low-dose radioiodine and possibly “downstaging” following an excellent response to primary therapy.