Introduction: According to a limited number of specialized hospital beds for radioiodine therapy in some countries, fractionated dose of radioiodine may be considered as the ablation therapy of differentiated thyroid cancer (DTC). Aim of the study was to compare the late effects of ablation therapy with single and fractionated dose of radioiodine in patients with DTC.
Patients and metods: Patients with DTC treated with one (131)I dose of 2.2 GBq or fractionated dose (1.1+1.1 GBq administered in 24-hour intervals) 516 weeks after thyroidectomy were retrospectively included.
Results: 83 patients treated with single dose and 186 treated with fractionated dose of radioiodine were included. There were no significant differences between the groups in male to female ratio, age at the time of the first (131)I administration, proportion of papillary thyroid cancers (P>0.05). Also the mean duration of follow-up did not differ significantly (8.0 vs. 7.8 years respectively, P=0.68). There were no significant differences including the course and outcomes of the treatment between the patients treated initially with single and fractionated dose of radioiodine. Cumulated doses were 7.5 vs. 7.0 GBq, second dose of radioiodine was administered in 55.4% and 54.8% of patients, mean number of (131)I administrations during the time of follow-up was 2.0 vs. 2.2 respectively. The overall survival (OS) did not differ significantly between the groups-five years OS was 98.6% for patients treated with single and 99.5% with fractionated dose of 131-I, 10 years 98.6 and 97.1% respectively.
Conclusions: The outcomes of treatment, expressed by percentage of patients needing second administration of radioiodine, mean number of administrations, cumulative dose of (131)I and probability of overall survival did not differ significantly. Treatment with fractionated doses (1.1+1.1 GBq) of (131)I administered in 24 hour intervals can be considered as equivalent alternative to the treatment with single dose of 2.2 GBq.