Decreasing the dose of radioiodine for remnant ablation does not increase structural recurrence rates in papillary thyroid carcinoma

Background. Our aim was to compare the rate of structural recurrence between patients who had lesser doses of radioactive iodine (RAI) and those who had traditional greater doses for remnant ablation after total thyroidectomy for papillary thyroid carcinoma (PTC). Methods. A retrospective cohort study of patients who had undergone thyroidectomy and RAI for PTC was undertaken. We divided the cohort into those who had <= 3 GBq (75 mCi) RAI (group A) and those who had >3 GBq (75 mCi) (group B). The primary outcome measure was the rate of structural recurrence. Results. Of 1,171 patients with PTC from 1990 to 2012 who were followed for a mean of 60 months, 970 with T1-T3 tumors underwent RAI in addition to thyroidectomy. The mean first dose of RAI was 2.5 GBq (68 mCi) for group A (n = 153) and 4.7 GBq (127 mCi) for group B (n = 817; P < .001). The overall rate of recurrence was 8%. When corrected for T stage, the recurrence rates were not different for T1 tumors (2% group A versus 4% group B; P = .54) nor for T2 and T3 tumors (P = .36 and .55, respectively). On multivariate analysis, the dose of RAJ was not an independent predictor for structural recurrence. Conclusion. Decreasing the dose of RAI at initial ablation for patients with pT1-pT3 PTC does not seem to be associated with an increased risk of structural cancer recurrence.