Fractionated Dosage of Radioiodine for the Ablation of Differentiated Thyroid Carcinoma

In some countries with a limited number of specialized hospital beds for radionuclide therapy, ablation therapy(RIT) of differentiated thyroid carcinoma (DTC) is performed using a fractionated dosage of radioiodine. The aim of this study was to evaluate the early clinical outcome of ablation with fractionated doses of RIT in comparison to the ablation with a single dose. A subset of 386 subjects with DTC referred for the initial RIT was selected retrospectively for the study. Of these, 113 patients (29.3%) were treated with one ¹³¹I dose of 2.2 GBq (group 1, RIT between 2001 and 2003) and 273 patients (70.7%) with fractionated doses (1.1 GBq + 1.1 GBq administered in 24 hour intervals) (group 2, RIT between 1999 and 2001). The early outcome of the initial RIT was evaluated 6–8 months later by radioiodine uptake test (RIU), thyroglobulin concentration, whole-body diagnostic scan, and neck ultrasound. On the basis of these results, the patients were classified as: CR, complete remission; NCR, no complete remission. Frequency of CR and NCR outcomes and the parameters measured during the follow-up evaluation in both groups were compared. CR outcome was found in 69 patients(61.1%) of group 1 and in 172 patients (63.0%) of group 2 (p = n.s.). No difference in measured parameters was found in both groups at the follow-up evaluation. In uncomplicated cases of DTC, RIT using a regimen of a fractionated dosage, is equally effective as the therapy with a single dose. No influence of stunning was observed in patients treated with a fractionated dosage, but the time interval between the doses was 24 hours.