Absorbed Dose Evaluation in Radioiodine Therapy with Different Approaches

The main approach to dierentiated thyroid cancer (DTC) therapy is still empiric, consisting of the administration of fixed activities. Repeated treatments, however, may have a stunning eect. An individualized dosimetric study may represent an important tool to determine the best activity to prescribe, in particular for patients with distant metastases or when therapy with recombinant human thyroid-stimulating hormone (rhTSH) stimulation is deemed necessary. This study provides a practical operational example for carrying out a dosimetric study, according to the European Directive EURATOM/59/13. Starting from the case of a patient who underwent rhTSH stimulation before radioiodine ablation, we illustrate the necessity of measuring both red marrow (RM) and blood (BL) absorbed dose during the treatment in order to not exceed the dose limit of 2 Gy to the RM, so as to avoid repeating radioiodine treatment several times. Dosimetry to the RM and BL was performed during the treatments, after administration of therapeutic activity without modifying the fixed activity schema, using dierent approaches. The results suggest the possibility of restricting the number of treatments, reducing thus the risk of stunning eect and, where possible, eliminating an additional source of stress and dejection for patients.