Purpose: To compare effectiveness of different radioiodine activities used for the treatment of benign thyroid disease.
Method: We retrospectively reviewed our local radioiodine audit data collected over 7 years duration. Patients with benign thyroid disease and known post-treatment biochemical outcomes were included. Data were analysed for primary diagnosis, activity dose, and biochemical outcomes in 6 and 12 months post-treatment.
Results: Over period of 7 years 276 patients received radioiodine therapy as primary or secondary treatment for benign thyroid disease. 249 of those have both radioiodine activity and biochemical outcomes known at the time of the study. Mean age was 54 years and 80% were females. Main indication for treatment was Hyperthyroidism (93%) of which 56% were Graves disease. Activity distribution was comparable with 46% of patients receiving 600 Mbq, 39% had 400 Mbq, and only 15% of other activities (500 or 800 Mbqs). Overall cure rate measured as the number of patients achieving euthyroidism or hypothyroidism post radioiodine therapy, was 88% in six months and 89.5% at 12 months. When divided in to the two main activities; cure rate was 83.5% at 6 months for 400 Mbq, which remained the same at 12 months follow up. For 600 Mbq, the cure rate was 94% at six months with further improvement to 96% at 12 months. There was no significant between groups difference in pre-treatment antithyroid drug therapy, primary or secondary indication for treatment, duration of ATD withdrawal prior to radioiodine therapy, goitre size or smoking status.
Conclusion: On this sizable sample, fixed radioiodine activity of 600 Mbqs for the treatment of hyperthyroidism, was more effective than variable dose in achieving biochemical cure (96% compared to 83.5%). This finding was independent of the primary hyperthyroid pathology, pre-treatment with anti-thyroid drug therapy or goitre size.