SAT-335 Preventing unexpected cancellations in Thyroid Hormone Withdrawal Radioactive Iodine Therapy: Lessons from Case Series

Abstract Disclosure: H. Oh: None. M. Jeon: None. C. Kim: None. W. Kim: None. W. Kim: None. J. Ryu: None. T. Kim: None. Background: Radioactive active iodine (RAI) treatment is the essential treatment for advanced differentiated thyroid cancer patient. However, unforeseen complications arising from thyroid hormone withdrawal (THW) can lead to the cancellation of scheduled treatments. We aimed to identify cases of treatment discontinuation during THW-RAI therapy due to THW-related complication and to explore preventable causes for improving patient management. Methods: Between 2012 and 2024, 4,174 patients underwent THW-RAI therapy in Asan Medical Center. Among them, 39 did not complete the planned treatment. After excluding cases canceled for reasons unrelated to THW, 11 patients with unexpected medical issues from THW were analyzed. Results: The median age of the included patients was 65 years (range: 31–72), with 10 being male. The reasons for discontinuation were hyponatremia (1 case), abnormal liver function (1 case), abnormal renal function (3 cases), and concurrent liver and renal dysfunction (6 cases). The patient with hyponatremia had a history of thiazide diuretic use. Most cases of liver dysfunction were associated with prior use of herbal medications, while renal dysfunction was linked to diuretic or non-steroidal anti-inflammatory drug use, pre-existing conditions such as single kidney and diabetic nephropathy, or inadequate oral intake during low-iodine preparation. Notably, two cases of combined liver and renal dysfunction were attributed to rhabdomyolysis following intense exercise or heavy workloads. Conclusions: Our analysis of 11 cases highlights avoidable factors that led to discontinuation of THW-RAI therapy. Enhanced patient education, comprehensive pre-treatment evaluations, and careful avoidance of high-risk medications are critical for minimizing disruptions in RAI therapy. Presentation: Saturday, July 12, 2025