Endocrine Abstracts

Background: Radioiodine (RAI) has been used for the treatment of hyperthyroidism for over half a century without agreement about its dose or regime. Following our previously presented audit, over the last three years we have used a 400MBq fixed dose (FD) RAI regime for the management of patients with hyperthyroidism, replacing the calculated dose (CD) regime.

Aim: To compare the cure rate following the use of a 400MBq fixed dose RAI regime with that achieved following the use of calculated dose method.

Patients and Methods: Patient information was obtained from the RAI database maintained at our centre since 1995. From 1995 to 2002 the previously described CD method, based on the 24-hour RAI uptake, was used. In 2002, this was changed to a fixed dose method using 400 MBq for all patients irrespective of pre-treatment factors. Thyroid function was checked at 6 weeks and at 3, 6 and 12 months following RAI therapy. Redosing was considered for patients who remained hyperthyroid at 6 months. Cure was defined as achieving euthyroid or hypothyroid state. 135 patients receiving FD were compared with 86 patients receiving CD for cure rate at 6 and 12 months following administration of RAI and frequency of redosing.

Results: A significantly higher percentage of patients treated with FD method were cured as compared to patients treated with CD method both at 6 months (85% v 74% respectively, P<0.05) and at 12 months (95% v 80%, P<0.05). The rate of redosing was lower with FD method (8% v 23%, P<0.05). These superior outcomes with the FD method were achieved at the cost of a higher final total RAI dose (432 MBq v 304 MBq, P<0.05).

Conclusion: Fixed dose RAI regime achieves higher rate of cure for hyperthyroidism as compared with the calculated dose regime, avoiding the inconvenience of redosing.