Selective use of radioactive iodine therapy for papillary thyroid cancers with low or lower-intermediate recurrence risk

Context: Current guidelines recommend a selective use of radioiodine treatment (RAI) for papillary thyroid cancer (PTC). Objective: To determine how policy changes affect the use of RAI and the short-term outcomes of patients. Design: Retrospective analysis of longitudinal data. Setting: Academic referral center. Patients: Patients with non-aggressive PTC variants; no extrathyroidal invasion or limited to soft tissues, no distant metastases, and ≤5 central-compartment cervical lymph node metastases. In Cohort 1, standard treatments were total thyroidectomy and RAI (May 2005-June 2011); in Cohort 2 decisions on RAI were deferred for ~12 months after surgery (July 2011-December 2018). Propensity score matching was used to adjust for sex, age, tumor size, lymph node status, and extrathyroidal extension. Intervention: Immediate RAI or deferred choice. Main outcome measures: Responses to initial treatment in ≥3 years of follow-up. Results: In Cohort 1, RAI was performed in 50/116 patients (51.7%), while in Cohort 2, it was far less frequent: immediately in 10/156 (6.4%), and in 3 more patients after the first follow-up data. The frequencies of structural incomplete response were low (1-3%), and there were no differences between the two cohorts at any follow-up visit. Cohort 2 patients had higher rates of "gray-zone responses" (biochemical incomplete or indeterminate response). Conclusions: Selective use of RAI increases the rate of patients with "uncertain" status during early follow-up. The rate of structural incomplete responses remains low regardless of whether RAI is used immediately or not. Patients should be made aware of both the advantages and drawbacks of omitting RAI.