Ethiodized oil interference of planned radioiodine therapy post thoracic duct embolization: report of 2 cases.

Radioiodine (RAI) therapy is considered in differentiated thyroid cancers (DTC) following surgery. While rare, a severe chyle leak (CL) resulting from surgery may require treatment with thoracic duct embolization (TDE) following lymphangiography. These procedures involve the administration of ethiodized oil into the central lymphatics. Herein, we present 2 cases-a 67-year-old man and a 21-year-old woman-diagnosed with papillary thyroid cancer who, following total thyroidectomy and neck dissection, developed a postoperative CL that was treated with TDE. Despite 12 weeks between TDE and evaluation for RAI therapy in both cases, nonradioactive iodine from ethiodized oil resulted in an excess urinary iodine concentration, potentially significant interference of RAI uptake, decreased diagnostic sensitivity, and reduced therapeutic efficacy. The 67-year-old man was evaluated for RAI therapy twice but did not receive treatment, whereas the 21-year-old woman received RAI therapy at initial evaluation despite excess iodine present. Potential interference of ethiodized oil on RAI imaging and therapy should be considered when selecting treatment for a severe CL and when evaluating the utility of RAI therapy after lymphatic interventions involving ethiodized oil.