Personalization of radioiodine treatment for Graves' disease: a prospective, randomized study with a novel method for calculating the optimal 131I-iodide activity based on target reduction of thyroid mass.

AIM

There is no consensus regarding the most appropriate dosimetric approach to cure Graves' disease. This study describes a personalized approach based on the desired therapy-induced volume (mass) reduction in order to define the activity of 131I-iodide to be administered, based on the MIRD approach and the radiobiological Linear Quadratic Model.

METHODS

A model for calculating the "optimal" final thyroid mass has been developed and published in the past years. Based on this model, it is possible to predict the thyroid absorbed dose following administration of a certain activity as a function of desired reduction of the starting mass of the gland. A total of 147 Graves' disease patients were randomly divided into four groups based on the absorbed thyroid dose, respectively 100 Gy (Group A, N.=29), 200 Gy (Group B, N.=25), and 400 Gy (Group C, N.=29), while patients of Group D (n=64) received a 131I-iodide activity calculated based on the desired "optimal" final thyroid mass.

RESULTS

At one-year follow-up, 48% of patients in Group A, 64% in Group B, 97% in Group C, and 94% in Group D were cured. There was no statistical difference between cure rate in Group C versus Group D. The administered 131I-iodide activity for Group C was significantly higher than for Group D (524 ± 201 MBq versus 386 ± 173 MBq, P<0.001).

CONCLUSION

These results demonstrate that the proposed method allows to optimize 131I-iodide therapy for Graves' disease patients on an individual basis, avoiding the administration of unjustified higher activities.