Endocrinol Metab.  2020 Sep;35(3):602-609. 10.3803/EnM.2020.741.

Clinical Outcomes of N1b Papillary Thyroid Cancer Patients Treated with Two Different Doses of Radioiodine Ablation Therapy

• Jin M
• Ahn J
• Lee YM
• Sung TY
• Kim WG
• Kim TY
• Ryu JS
• Kim WB
• Shong YK
• Jeon MJ

• KMID: 2508010
• DOI: http://doi.org/10.3803/EnM.2020.741

Abstract

Background
The optimal dose of radioactive iodine (RAI) therapy for N1b papillary thyroid carcinoma (PTC) is controversial. We evaluated the clinical outcome of N1b PTC patients treated with either 100 or 150 mCi of RAI.
Methods
We retrospectively analyzed N1b PTC patients who underwent total thyroidectomy and postoperative RAI therapy at a tertiary referral center between 2012 and 2017. As the baseline characteristics differed between treatment groups, we performed exact matching for various pathological factors according to RAI dose. We evaluated the response to therapy and recurrence-free survival (RFS) in the matched patients. Structural recurrent/persistent disease was defined as new structural disease detected after initial therapy, which was confirmed by cytology or pathology.
Results
Of the total 436 patients, 37 (8.5%) received 100 mCi of RAI and 399 (91.5%) received 150 mCi of RAI. After an exact 1:3 matching, 34 patients in the 100 mCi group and 100 patients in the 150 mCi group remained. There was no significant difference in response to therapy between the groups in the matched population (P=0.63). An excellent response was achieved in 70.6% (n=24) of patients in the 100 mCi group and 76.0% (n=76) in the 150 mCi group. Two (5.9%) patients in the 100 mCi group and four (4.0%) in the 150 mCi group had recurrence and there was no significant difference in RFS between the groups in the matched population (P=0.351).
Conclusion
There were no differences in response to therapy and RFS in N1b PTC patients according to RAI dose.

Keyword

Thyroid neoplasms; Neoplasm metastasis; Recurrence

Figure

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  Fig. 1 Flow chart of patient enrollment. PTC, papillary thyroid carcinoma; RAI, radioactive iodine.

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  Fig. 2 Kaplan-Meier analysis of recurrence-free survival according to different doses of radioactive iodine (RAI) therapy. (A) Recurrence-free survival in total 436 patients. (B) Recurrence-free survival in the matched 134 patients according to different doses of RAI.

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