30mCi radioactive iodine achieving comparative excellent response in intermediate/high-risk nonmetastatic papillary thyroid cancer: a propensity score matching study

Objective To determine the efficacy of low-dose radioactive iodine (RAI) therapy (30 mCi, 1110 MBq) in Chinese patients with intermediate- to high-risk papillary thyroid cancer (PTC) without distant metastasis. Design and methods This large retrospective study included Chinese patients with PTC that tested negative for thyroglobulin antibodies. Patients were categorized into low-dose (30 mCi, 1110 MBq) and high-dose (>100 mCi, 3700 MBq) RAI groups. Ablation rate and long-term response were compared between groups using propensity score matching (PSM) to minimize bias and confounding. Results In total, we included 446 patients. No significant difference in ablation success rate was found between groups ( P = 0.305) before or after PSM ( N = 162; P = 0.200). Excellent response (ER) rate was not significant between groups before ( P = 0.917) or after PSM ( P = 0.798). Efficacy of low-dose RAI was similar to that of high-dose RAI in N0- ( P = 1.000), N1a- ( P = 0.981), and N1b-stage ( P = 0.903) patients. Low- and high-dose RAI groups achieved similar ER rates in pre-ablative stimulated thyroglobulin level (≤1 ng/mL, P = 1.000; 1 < ps-Tg ≤ 5 ng/mL, P = 0.444; 5 < ps-Tg ≤ 10 ng/mL, P = 0.665; >10 ng/mL, P = 1.000) and BRAF V600E -positive ( P = 0.324) subgroups. Conclusions Efficacy of low-dose RAI therapy was similar to that of high-dose for ablation and achieving ER in Chinese nonmetastatic intermediate- to high-risk PTC patients. High-dose RAI could not rectify ablation failure or non-ER rates in PTC patients with BRAF V600E , lymph node metastases, or unfavorable thyroglobulin levels.