No evidence of chromosome damage in children and adolescents with differentiated thyroid carcinoma after receiving I-131 radiometabolic therapy, as evaluated by micronucleus assay and microarray analysis

Purpose As I-131 therapy, used to achieve ablation of thyroid gland remnant, can cause chromosome damage in cultured peripheral lymphocytes especially, we investigated whether administration of radioiodine may induce early genome damage in peripheral T lymphocytes of adolescents with differentiated thyroid carcinoma (DTC). Methods We studied 11 patients, aged 14.8 +/- 3.1 years, who assumed I-131 (range: 1.11-4.44 GBq) to ablate thyroid remnant. A blood sample for micronucleus assay and for evaluating expression of some genes involved in the DNA repair or the apoptosis pathways was obtained from each patient 1 h before (T-0) and 24 (T-1) and 48 h (T-2) post-radioiodine administration. Results Compared to T-0, we did not find any difference in the number of micronucleated cells at both T-1 and T-2 in any subject. Nine out of 11 patients had altered expression levels in a majority of the DNA repair and apoptosis genes at T-1, which decreased at T-2. Conclusions We demonstrated for the first time that peripheral cells of DTC children and adolescents who received I-131 at a mean dosage of 3.50 +/- 0.37 GBq did not show chromosome damage within 48 h from the end of radiometabolic therapy. This may be due to a prompt activation of the cell machinery that maintains the integrity of the genome to prevent harmful double-strand breaks from progressing to chromosome mutations, either by repairing the lesions or by eliminating the most seriously damaged cells via apoptosis.