I-131 therapy in patients with benign thyroid disease does not conclusively lead to a higher risk of subsequent malignancies

Due to its excellent tolerability and low incidence of side effects,I-131 therapy has been the treatment of choice for benign thyroid diseases for over 60 years. A potentially increased risk of malignancies due to this therapy is however still subject of debate. Aim: To review the literature pertaining to I-131 therapy of benign thyroid diseases in order to establish whether there is an increased incidence of, or increased mortality due to malignancies of the thyroid or other organs. Methods: In order to allow for sufficient long-term follow-up time after I-131 therapy, only literature after 1990 was reviewed. Two criteria were applied to consider an increased incidence of malignancies linked to I-131 therapy: a) there should be a latency period of at least 5 years between I-131 therapy and the observation of an increased risk b) an elevated risk should increase with increasing radiation exposure. Results:A total of 7 studies reporting cancer incidence and / or mortality in 4 different patient collectives spanning a total of 54510 patients over an observation period varying from 2-49 years were found. Although some studies detected a slightly increased risk for malignancies of the thyroid or the digestive system, others did not find these effects - while other studies even reported a slightly lower risk of malignant (thyroid) disease after I-131 therapy for benign thyroid diseases. Conclusion: As over 60 years of experience has thus far failed to produce conclusive evidence to the contrary, it can be concluded that there is no increased risk of malignancies after I-131 therapy for benign thyroid disease.