Fractionated Dosage of Radioiodine for the Ablation of Differentiated Thyroid Carcinoma

Abstract

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 (131)I 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.