Endocrine Abstracts (2011) 26 OC4.5

Comparison of four strategies of radioiodine ablation in patients with thyroid cancer with low-risk of recurrence: the randomized, prospective ESTIMABL study

L Leenhardt1, B Catargi2, I Borget3, S Zerdoud4, B Bridji5, S Bardet6, M E Toubert7 & M Schlumberger8

1Endocrinology Department, Pitie Salpetriere, Paris, France; 2Endocrinology Department, CHU Bordeaux, Bordeaux, France; 3Biostatistic and Epidemiology Service, Nuclear Medicine and Endocrine Oncology, Institut Gustave Roussy, Villejuif, Paris, France; 4Nuclear Medicine Department, Institut Claudius Regaud, Toulouse, France; 5Nuclear Medicine Department, Centre René Gauducheau, Nantes, France; 6Nuclear Medicine Department, Centre François Baclesse, Caen, France; 7Nuclear Medicine Department, Hopital Saint-Louis, Paris, France; 8Nuclear Medicine and Endocrine Oncology, Institut Gustave Roussy, Paris, France.

Objective: The objective of this clinical trial is to compare four strategies of management of postoperative radioiodine ablation in a 2×2 factorial design, each strategy combining a method of TSH stimulation and an activity of 131I. The primary endpoint is the rate of thyroid ablation.

Patients and methods: This multicentric, randomized, controlled, phase III trial involved 24 French centers, and compared 4 strategies for postoperative radioiodine ablation in a 2*2 factorial design: a method of TSH stimulation (either thyroid hormone withdrawal (THW) or rhTSH (Thyrogen, Genzyme)) and an activity of 131I (either 1.1 or 3.7 GBq). Study patients met the following criteria: age >18 years; total thyroidectomy for differentiated papillary or follicular (no aggressive histology) thyroid carcinoma, between 30 and 120 days before randomization, treatment with L-T4 for at least one month; TNM stage pT1<1 cm, N1 or Nx, pT1>1 cm (any N) or pT2, N0; absence of distant metastasis, no iodine contamination. Thyroid ablation was assessed at 6–10 months after radioiodine ablation with rhTSH stimulated Tg determination and neck-US; whole-body scan was performed in case of positive Tg antibodies (TgAb). The comparison between the four strategies is based on equivalence framework, with two-side α=0.05.

Results: Seven hundred and fifty-three patients who gave written informed consent were included in the study between April 2007 and February 2010 and currently data on radioiodine ablation are available for 693 patients (92%) who form the basis of the present report: 79% were females, mean age was 49 years, and 90% had papillary cancer; 30% of tumors were pT1N0, 17% were pT1N1, 39% were pT1, Nx and 12% were pT2, N0. Mean time between thyroidectomy and randomization was 50 days, and mean time between randomization and radio-iodine ablation was 39 days. Data on the follow-up control are currently available for 477 patients. Neck-US was normal in 444 patients (93%) and suspicious or abnormal in 33 (7%). Stimulated Tg level was >1.0 ng/ml in 25 (5%) patients and 31 patients had TgAb. Thyroid ablation was considered complete in 417 patients (87%), incomplete or doubtful in 58 patients (12%) and non-evaluable in 2 patients.

Conclusion: These data will be updated for the ECE meeting, and results of ablation will be presented.

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