The Dose of Radioactive Iodine Needed to Ablate the Thyroid Remnant Left Behind After Thyroidectomy

Phase 3

• Conditions: Thyroid Neoplasms
• Interventions: Drug: Radioactive iodine

• Registration Number: NCT00115895
• Lead Sponsor: University of Helsinki

Brief Summary

The thyroid cells take up iodine, and radioactive iodine is commonly used to irradiate residual thyroid tissue and thyroid cancer following surgical removal of the thyroid gland (thyroidectomy). A whole body radioactive iodine scanning is usually carried out after thyroidectomy to assess the amount of thyroid tissue left behind at surgery (that might still contain cancer), and to evaluate the presence of iodine avid lesions elsewhere in the body (that might be cancer metastases). A large dose of radioactive iodine is often given, still the optimal iodine dose to ablate the thyroid remnant after surgery is not known. In this study, two radioactive iodine doses are compared in the ablation of the thyroid remnant, a smaller (1110 MBq) dose and a larger (3700 MBq) dose. The study participants are randomly allocated using a 1:1 ratio to receive either the smaller or the larger radioactive iodine dose. These treatments are compared for safety, adverse effects, and the need for subsequent repeat treatments. The individual absorbed radiation doses are measured. The study hypothesis is that fewer repeat radioiodine treatments might be needed after the larger dose, but the larger dose might be associated with a higher frequency of adverse events.

Detailed Description

The study participants are randomly allocated to receive either a 1110 MBq or a 3700 MBq dose of radioiodine (131I) approximately 5 weeks after thyroidectomy. Thyroxin substitution is initiated only after administration of radioactive iodine. Treatment efficacy is monitored using serum thyroglobulin measurements and whole body radioiodine scanning. The absorbed radiation dose at the thyroid remnant and the biological half-life of radioactive iodine are measured with SPECT, 131I iodine detector and a Geiger counter.

Treatment related adverse events are collected using structured forms 4 to 5 days, 2 weeks and 3 months after administration of radioiodine. The need for a repeat treatment is assessed 4 to 6 months after the first administration of radioiodine. The criteria for a repeat radioiodine treatment are serum thyroglobulin \> 1 ug/L and/or presence of abnormal radioiodine uptake in a whole body radioiodine scanning, which is carried out following a 4-week interruption of thyroxin supplementation or following administration of rhTSH.

Number of patients: 160

Aims of the study:

* To find out weather the risk for second radioiodine treatment differs with two dose levels of radioiodine: 1110 MBq or 3700 MBq.

* To study possible differences in the adverse effects in the treatment groups. Also days at hospital are counted.

* To analyse the effect of absorbed radiation dose to the treatment results

Study Timeline

• Study Start: 2000-01
• Primary Completion: 2004-10
• Study First Submitted: 2005-06-26
• Study First Submitted QC: 2005-06-26
• Study First Posted: 2005-06-27
• Status Verified: 2018-03
• Last Update Submitted: 2018-03-01
• Last Update Posted: 2018-03-02
• Study Completion: 2020-09

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: All
• Target Recruitment: 160

Inclusion Criteria

Not provided

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Radioactive iodine 1,1 GBq	Radioactive iodine	Low activity of radioiodine, 1,1 GBq
Radioactive iodine 3,7 GBq	Radioactive iodine	Routine activity of radioiodine, 3,7 GBq

Primary Outcome Measures

Name	Time	Method
Cumulative number of radioactive iodine administrations	15 yrs

Secondary Outcome Measures

Name	Time	Method
Adverse events	15 yrs
Absorbed radiation dose	15 yrs
Cancer recurrence	15 yrs

Trial Locations

Locations (1)

Helsinki University Central Hospital, Department of Oncology; 🇫🇮 Helsinki, Finland