A38: Outcomes of radioiodine remnant ablation in differentiated thyroid cancer
1Gloucestershire Hospitals NHS Foundation Trust, Gloucestershire, UK
Radioiodine remnant ablation (RRA) is performed as adjunct to total thyroidectomy in patients with differentiated thyroid cancer to facilitate the use of the tumour marker thyroglobulin (Tg) for long term monitoring and reduce recurrence in selected cases. Currently success of RRA is assessed by diagnostic 131I (Radioactive Iodine 131)whole body scan (WBS) and stimulated thyroglobulin (sTg) levels at 6-9 months as per the HiLo trial.
The results of the WBS and sTg levels in patients who received 1.1 GBq (low risk) and 3.7 GBq (intermediate risk) after 6 months of RRA between April 2012 to March 2014 were reviewed. Success of ablation (negative scan and sTg levels < 2.0ug/l at 6 months) and details of retreatment were compared to the HiLo trial results
31 patients received 1.1 GBq and 36 patients received 3.7 GBq dose of 131I.We excluded 7 patients (4-poorly differentiated, 1-metastasis,1-R1 resection, 1- had no WBS scan) out of total 67 patients to represent similar baseline characteristics as the HiLo trial. Ablation success based on WBS alone was 85%, based on sTg alone 90%, and based on both 76.6% - comparable to the HiLo trial. 7/30 patients (23.3%) who received 1.1GBq were given repeat treatment after 3 months of first treatment as compared with 3/30(10%) received 3.7 GBq. Only 7 of the re-treated patients were the post ablation uptake scans positive.
Our results are comparable to the HiLo trial outcomes. Assessing success of RRA at 6 months however leads to false positive results. Performing the WBS/sTg at 9 months, would have avoided retreatment in 3 out of 10 patients. This has led us to change our practice of WBS and sTg to 9 months post RRA.