Trial Information

Effect of the Radioiodine Dose in Thyroid Ablation- A Randomized Comparison of 1110 MBq to 3700 MBq

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