Implications of 123I whole body scan pre-ablation of thyroid remnant in papillary thyroid cancer patients

311 Objectives The use of 123I whole body scan (WBS) before 131I radioiodine ablation (RIA) of the post-surgical thyroid remnant in patients with papillary thyroid cancer (PTC) remains debated. The ATA’s guidelines state that WBS may be useful before RIA. Some institutions do not require the use of WBS as part of the protocol. We therefore evaluated the impact of WBS prior to ablation of thyroid remnant in patients with PTC. Methods We reviewed 117 consecutive patients with PTC who had total thyroidectomy and were referred for RIA between Aug 2007 - Feb 2009. There were 84 women and 33 men, 13-82 year-old (average: 45.5). Three endocrinologists blinded to the results of the WBS reviewed patients’ data including sex, age, pathology, Tg, anti-Tg, TSH and ultrasound. Each then returned the RIA dose that each patient would have received, based on the following rules: 50-75 mCi (remnant only); 75-125 mCi (lymph nodes metastases); 150 mCi (lung metastases) and 200 mCi (bone metastases). We compared their recommended doses with the actual RIA doses prescribed after analyzing the WBS. Results The dose prescribed by the endocrinologists matched the dose administered after analyzing the WBS in 59 patients (50.4%). However, for 31 patients (26.5%) the endocrinologists would have given a lower dose and for 25 patients (21.4%) a higher dose than administered based on the results of the WBS. The endocrinologists recommended doses in disagreement with each other in 2 patients (1.7%). In the group of patients who would have received a higher dose there were 8 patients that were not treated after analyzing the WBS: 4 of them had no abnormal iodine uptake and the other 4 had breast uptake. Conclusions Our study suggests a significant role of the pre-therapy WBS in PTC patients referred for RIA post-thyroidectomy. The actual RIA dose that was administered based on the WBS differed from the dose suggested in the absence of the WBS in 49.6% of the cases.