Efficacy of low-dose radioactive iodine ablation with rhTSH in differentiated thyroid carcinoma

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 459-496-Thyroid Neoplasia & Case Reports
Clinical
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-477
Na Kyung Kim*1, Ji Young Joung1, Yoon Young Cho1, Seo Young Sohn1, Hye Jeong Kim1, Hyun Kyung Tan1, Yun Jae Chung2, Sun Wook Kim1 and Jae Hoon Chung1
1Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea, 2Chung-Ang University College of Medicine, Seoul, South Korea
Background : Recently, two multicenter, prospective studies have reported that low-dose radioactive iodine (RAI) was as effective as high-dose RAI for treating patients with differentiated thyroid carcinoma, regardless of using either recombinant human TSH (rhTSH) or thyroid hormone withdrawal (THW) before ablation. This study was conducted to confirm the efficacy of low-dose RAI ablation with rhTSH compared to THW in Korean patients with differentiated thyroid carcinoma.

Subjects & Methods : The retrospective study was designed to compare the efficacy of rhTSH with THW before ablation in low-dose RAI (30 mCi) ablation as well as high-dose (100 mCi) ablation. A total of 576 patients [ papillary thyroid carcinoma 564 (98%); rhTSH 192 vs. THW 384] were enrolled, who had TNM stage, T1 to T3, N0 to N1, and M0. Patients underwent THW were selected twice in number as age, gender, T-stage and N-stage matched patients. The successful ablation was defined as stimulated serum thyroglobulin (Tg) less than 1 to 2 ng/mL with undetectable serum anti-Tg antibody or absence of significant visible uptake above background activity in the neck on diagnostic whole-body scan (DxWBS) at 6 to 12 months after first RAI ablation. The successful ablation rates were estimated in each group under the five criteria: Criteria 1 (negative DxWBS), 2 (Tg <2 ng/mL), 3 (Tg <2 ng/mL & negative DxWBS), 4 (Tg <1 ng/mL), and 5 (Tg <1 ng/mL & negative DxWBS). We allowed maximum differences within 10% between rhTSH and THW. All 95% confidence intervals for the differences were within -10%, indicating noninferiority.

Results : When only negative DxWBS was chosen as a successful criterion in patients administered with low-dose RAI, successful ablation rates were 80.5% in patients with rhTSH compared to 79.9% with THW (p=0.91). When only stimulated serum Tg level less than 2 ng/mL was considered as a successful criterion, they were 95.4% in patients with rhTSH compared to 92.5% with THW (p=0.40). When both of stimulated serum Tg level (<2 ng/mL) and negative DxWBS were selected as successful criteria, they were reduced to 79.3% in patients with rhTSH compared to 75.9% with THW (p=0.53). When only stimulated serum Tg level less than 1 ng/mL was considered as a successful criterion, they were 89.6% in patients with rhTSH compared to 86.2% with THW (p=0.42). When both of stimulated serum Tg level (<1 ng/mL) and negative DxWBS were selected as successful criteria, they were reduced to 77.0% in patients with rhTSH compared to 71.3% with THW (p=0.32). Therefore, low-dose RAI ablation in patients with rhTSH was as effective as THW, using any criteria of successful ablation.Similar results were found in the efficacy of high-dose RAI ablation in patients with rhTSH compared to THW, using any criteria of successful ablation.

Conclusion : Low-dose RAI ablation with rhTSH was as effective as THW before ablation in Korean patients with differentiated thyroid carcinoma.

Nothing to Disclose: NKK, JYJ, YYC, SYS, HJK, HKT, YJC, SWK, JHC

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm