Radioiodine Clearance and Quality of Life in Thyroid Cancer Patients with Radioiodine Ablation: A Comparison between Thyroid Hormone Withdrawal and Recombinant Human Thyroid Stimulating Hormone Injection

Background: Both thyroid hormone withdrawal (THW) and recombinant human thyroid stimulating hormone (rhTSH) can effectively stimulate thyroid stimulating hormone (TSH) before radioiodine thyroid remnant ablation. Our aim was to compare the iodine biodistribution, and radiation exposure dose rate with the use of both regimens. Methods: Seventy-seven thyroid cancer patients (55 THW, 22 rhTSH) with previous diagnostic images that proved thyroid remnants were recruited for the study. All patients received 3.7 GBq (100mCi) of I-131 at 6 wk after THW, or 3d after 1st rhTSH administration. Dose rates were assessed at 1, 5, 16, 21, 27, and 40 h. For biodistribution study, sixty-seven subjects (44 THW, 23 rhTSH) were assessed by additional whole body scans at day 3, 5, and 8 post-ingestion. Results: The total-body effective half-life of radioiodine calculated from the dose rate was significantly prolonged in patients who received THW as compared to rhTSH (9.93 h vs. 7.53 h). The biodistribution result from scintigraphic analysis showed that the effective half-life remnant was similar in both groups, although the values were numerically longer in the rhTSH arm. Inversely, the values were shorter in the rest of the organs of the rhTSH subjects. The quality of life result from questionnaire analysis showed that in terms of THW versus rhTSH; cold intolerance (87% vs. 57%), dizziness (76% vs. 59%), poor appetite (62% vs.50%), constipation (60% vs. 50%), slow movements (71% vs. 50%), and peri-orbital puffiness (60% vs. 50%).