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.