Introduction
The initial treatment options for Graves’ disease(GD) are anti-thyroid drugs(ATDs), radioactive iodine ablation(RAI) and surgery. The effects of these three modalities are similar. Thus, the choice of treatment was chosen by patient’s and physician’s preference. In Korea, most patients used ATDs as initial treatment, RAI tends to be used who failed with ATDs. For this reason, we estimated the first RAI success rate in Korea might be different from other countries.
Methods
The patients underwent the first RAI between January 2007 and January 2017. A total of 247 patients were enrolled, primary outcome was a cumulative success rate in the first year, and factors affecting the success rate. Secondary outcome was delayed response, which is a patient who reached successful RAI during the follow-up period after the first year, and factors affecting the delayed response.
Results
The cumulative success rate in the first year was 62.8%. On multivariate analysis, recur(Reference(Ref) is recur; HR 0.074, P<0.001), duration of using ATDs(Ref ≤1yr; < 1yr to ≤ 5yr, HR 0.454, P=0.001; 5yr <, HR 0.062, P<0.001), size of goiter(Ref ≤ 45g; 45g <, HR 0.512, P=0.027), and fT4 after RAI(Ref ≤ upper normal range(UNL); 1.5*UNL <, HR 0.405, P=0.006) was associated with the RAI success. Twenty-seven patients were showed delayed response, and pre-RAI TRAb (P=0.003) and post-RAI fT4 (P=0.005) were affecting to delayed response.
Conclusions
The success rate of the first RAI in Korea was lower than other countries, and most of the affecting factors were related to disease severity. In Korea, a patient who received RAI might be more “refractory” case than other countries because of medical accessibility and physician’s preference. The delayed response was observed in patients with low pre-RAI TRAb and low post-RAI fT4. In these patients, clinical follow-up with careful monitoring could be an option for the treatment.