High-dose radioactive iodine therapy is associated with decreased risk of recurrence in high-risk papillary thyroid cancer

Objectives We aimed to determine the effect of adjuvant radioactive iodine dose on recurrence rate in high-risk papillary thyroid cancer. Methods More than 1,500 patients treated for papillary thyroid cancer at high-volume centers in France and the United States from 2004–2014 were reviewed. Patients considered at high risk for recurrence per the 2015 American Thyroid Association guidelines were analyzed and grouped by initial radioactive iodine dose: intermediate (median 100 mCi) or high dose (median 150 mCi). Propensity score matching was performed to control for baseline characteristics. Results In a propensity-matched cohort of 66 patient pairs, there were equivalent rates of gross extrathyroidal extension (71% vs 71%, P = 1.00), positive margins (55% vs 55%, P = 1.00), lymph node metastases ≥ 3 cm (9% vs 9%, P = 1.00), extranodal extension (32% vs 33%, P = .85), and distant metastases (2% vs 5%, P = .31). Over a median follow-up of 4.5 years (interquartile ratio 2.0–7.5 years), the intermediate-dose radioactive iodine group had a significantly higher rate of recurrence than patients in the high-dose radioactive iodine group: 24 out of 66 (36%) vs 13 out of 66 (20%), P = .03. Conclusion High-dose radioactive iodine is associated with lower recurrence rate compared with intermediate-dose radioactive iodine for patients with American Thyroid Association high-risk papillary thyroid cancer.