Radioiodine Therapy Induced Cytotoxicity in Patients with Differentiated Thyroid Carcinoma

Cytological radiation damage to lymphocytes can result in augmentation of cells with micro-nuclei. In this study we investigated cytological radiation damage to peripheral blood lympho-cytes using the the micronuclei assay (MNA) me-thod, considering the value of 131I in diagnostic and therapeutic nuclear medicine and high ab-sorbed dose of 131I radioiodine in comparison with gamma emitters and the effect of type of radiation, dose and species on radiosensitivity of patient. At present no similar investigation from Iran has been reported evaluating the cytological radiotoxicity of therapeutic radiotracers such as 131I. Materials and Methods: We studied 22 patients with differential thyroid carcinoma referred for treatment with 100 or 150 mci 131I. Peripheral lymphocytes were harvested and isolated by a cytological method and assayed for frequency of micronuclei as a marker of cytological radiotox-icity before and one week after treatment. Results: The means for micronuclei per one hundred binuclear lymphocytes were 6. 3±2.2 be-fore treatment and 9. 6±3.1 after treatment. These differences in the number of micronuclei was statistically significant (p<0. 05). Conclusions: High doses of radioiodine therapy used after surgery in differentiated thyroid car-cinoma can increase micronuclei among peri-pheral lymphocytes as an indirect marker of chromosomal aberrations and cytotoxic radiation damage.