rhTSH-Thyroid Ablation With 1850 MBq of 131I
Condition: Thyroid Cancer
MeSH terms: Thyroid Neoplasms; Thyroid Diseases
Study type: Observational

Summary: 
      Most patients with differentiated thyroid carcinoma (DTC) are treated with therapeutic doses
      of radioiodine (131I) after initial surgery (total or near total thyroidectomy), aimed to
      destroy microscopic residual normal or tumoral thyroid cells and to facilitate the early
      detection of tumor recurrence based on serum thyroglobulin (Tg) measurement and 131I whole
      body scan (WBS) (1-5). Recently, preparation of patients for thyroid ablation with rhTSH and
      3700 MBq of 131I on l-thyroxine (l-T4) therapy has been approved in Europe by the European
      Medicines Agency (EMEA) as an alternative to thyroid hormone withdrawal (6), after a
      randomized, controlled, multicenter study demonstrated that both methods of preparation are
      equally effective (with 100% rate of successful ablation) and that patients prepared with
      rhTSH received lower total body irradiation and experienced a better quality of life compared
      to those rendered hypothyroid (7).

      The present study was aimed to compare the efficacy of fixed activities of 1850 MBq versus
      3700 MBq of 131I for post surgical thyroid ablation in DTC patients prepared with rhTSH
      (TSHα, Thyrogen®, Genzyme Therapeutics, Cambridge, MA) on l-T4 therapy.
    

Detailed description: 
      Aim: Recently, a multicenter study in differentiated thyroid cancer (DTC) patients showed
      that 3700 MBq of 131I after rhTSH stimulation had successful post-surgical thyroid ablation
      rate similar to that obtained after thyroid hormone withdrawal. We investigated whether 1850
      MBq of 131I have a rate of successful ablation similar to 3700 MBq in patients prepared with
      rhTSH.

      Methods: Seventy-two patients with DTC were randomly assigned after surgery to receive 1850
      MBq (group A, n: 36) or 3700 MBq (group B, n: 36) of 131I after rhTSH. The two groups were
      comparable for age, sex, histotype and tumor stage. One injection of 0.9 mg of rhTSH was
      administered for two consecutive days; 131I therapy was delivered 24 hours after the last
      injection. A post-therapy whole body scan (WBS) was performed 72 hours later. Successful
      ablation was assessed 6-8 months after therapy.

      Results: Successful ablation, defined as no visible uptake in the diagnostic WBS after rhTSH
      stimulation, was achieved in 88.9% of group A and group B patients. Basal and
      rhTSH-stimulated serum Tg was undetectable (<1 ng/ml) in 88.6 % of group A and 84.8% of group
      B patients (p=0.65). Similar rates of ablation were obtained in both groups also in patients
      with lymph node metastases. Dosimetric data showed similar thyroid bed uptake, effective
      half-life and adsorbed dose in the two groups. Failure to ablate was not correlated with TNM
      staging, peak TSH levels, thyroid bed uptake and urinary iodine excretion at the time of
      ablation, but was influenced by the absorbed dose of 131I (< or >300 Gy).

      Conclusion: Our results demonstrate that therapeutic 131I activities of 1850 MBq are equally
      effective as 3700 MBq for thyroid ablation in DTC patients prepared with rhTSH, even in the
      presence of lymph node metastases.
    

Intervention name(s): radioiodine therapy after rhTSH
Intervention type(s): Procedure
Observational model: Natural History
Time perspective: Prospective
Keywords: thyroid cancer; rhTSH; thyroid ablation