Early Dynamic Risk Stratification Decreases Rate of Ablative and Adjuvant Radioiodine Use in ATA Low and Intermediate Risk Papillary Thyroid Cancer Patients.

Objectives: In differentiated thyroid cancer (DTC), radioiodine (RAI) therapy is most frequently employed for remnant ablation or as adjuvant therapy for the remaining disease. The application of RAI to patients classified as intermediate risk (InR) is still a matter of debate. The aim of this study is to analyze the effect of early postoperative risk assessment on RAI use on papillary thyroid cancer patients who are classified as low risk (LoR) or InR.

Methods: This is a single-center, prospective registry study. One-hundred-eighty-six patients operated between January 2012 and August 2021 and categorized as LoR or InR were included in this study. All patients had total thyroidectomy and central lymph node dissection by the same endocrine surgeon. An early dynamic risk assessment (EDRA) consisting of neck ultrasonography, serum thyroglobulin (Tg) and anti-Tg levels was performed 6 weeks after surgery. Most of the patients were either followed up without RAI or received ablative low activity (30-50 mCi) RAI based on predetermined criteria.

Results: Median follow-up was 63 months. Sixty-six (61%) patients in the LoR group and 43 (56%) patients in the InR group did not receive RAI treatment. Thirty-eight (35%) and 22 (29%) patients in LoR and InR groups received ablative (30-50 mCi) RAI therapy, respectively. In LoR group 5 (4.6%) patients and in InR group 12 (16%) patients received 100 mCi or more RAI activity. Only one patient in the InR group recurred during follow-up. No statistically significant difference regarding local recurrence was found between patients who didn't receive RAI or were treated with RAI within both LoR (p=0.152) and InR (p=0.272) groups.

Conclusion: There is consensus for LoR patients about omitting RAI therapy after surgery. Indications for RAI treatment in InR DTC are still under debate. RAI use based on EDRA seems to be a better option than decisions solely made on histopathological risk factors and decreases adjuvant high-activity RAI use without increasing recurrence risk.