Response to Surgery Assessments for Sparing Radioiodine Remnant Ablation in Intermediate-Risk Papillary Thyroid Cancer

Abstract

Abstract Context Using response to surgery when tailoring radioiodine (RAI) therapy for papillary thyroid cancer (PTC) is valued but lacks prospective validation. Objective To spare RAI thyroid remnant ablation among patients with intermediate-risk PTCs using 3-tiered assessments with response to surgery highlighted, in addition to the risk of the recurrence stratification and TNM staging. Methods Patients with no evidence of disease (NED) identified as excellent response (ER) or indeterminate response (IDR) to surgery were spared from RAI thyroid remnant ablation after informed consent and prospectively enrolled under active surveillance. Those involved in other trials or without sufficient follow-up data were excluded. Dynamic responses were followed and compared longitudinally. The main outcome measures were NED presenting as durable ER or IDR for over 12 months. Results Of the enrolled 215 patients, 47.4% (102/215) ER and 52.6% (113/215) IDR were identified regarding RAI decision-making. After a median of 23.6 (interquartile range 13.8-31.6) months, the share of ER increased to 82.8% (178/215) and IDR decreased to 16.3% (35/215), with 85 patients shifting from IDR to ER over time, only 0.5% (1/215) structural incomplete response and 0.5% (1/215) biochemical incomplete response observed. Successful remnant ablation was observed in 27.7% (26/94) of the patients completing 2 diagnostic whole-body scans after a median interval of 13.0 months, indicating a theranostic effect. In the 173 patients followed for over 12 months, the NED rate did not differ between ER and IDR subgroups (100% vs 97.9%, P = .20). Conclusion Through the 3-tiered assessments with response to surgery highlighted, postoperative ER and IDR spared from RAI remnant ablation may indicate similar favorable responses in intermediate-risk patients with PTC during 23.6 months of follow-up.