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

As 131I 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). We studied 11 patients, aged 14.8 ± 3.1 years, who assumed 131I (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 (T0) and 24 (T1) and 48 h (T2) post-radioiodine administration. Compared to T0, we did not find any difference in the number of micronucleated cells at both T1 and T2 in any subject. Nine out of 11 patients had altered expression levels in a majority of the DNA repair and apoptosis genes at T1, which decreased at T2. We demonstrated for the first time that peripheral cells of DTC children and adolescents who received 131I 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. (orig.)