Cytogenetic alterations and oxidative stress in thyroid cancer patients after iodine-131 therapy

This study aimed to assess two end-points of DNA damage, namely chromosomal aberrations and micronuclei in peripheral lymphocytes, and their possible relationship with oxidative stress (which may be related to DNA damage and repair) in thyroid cancer patients receiving therapeutic doses of I-131. Ni neteen patients receiving 2590 MBq (70 mCi) were studied. Chromosomal aberr ations were scored using standard cytogenetic methods and micronuclei score d in cytokinesis-blocked lymphocytes. Oxidative stress was assessed by dete rmining thiobarbituric acid-reactive substances in blood, total plasma anti oxidant status and serum uric acid levels. All parameters were assessed bef ore treatment and 1 and 6 months after I-131 administration, The frequency of micronucleated cells per 1000 binucleated cells scored (mean +/- SEM) in creased significantly from 5.21 +/- 0.80 to 9.68 +/- 1.22 1 month after tre atment (P < 0.01) and to 8.42 +/- 1.28 6 months after treatment (P < 0.05), The frequency of cells with chromosomal aberrations, excluding gaps, per 1 00 cells, increased significantly from 1.68 +/- 0.41 to 3.47 +/- 0.55 1 mon th after treatment (P < 0.01) and to 4.05 +/- 0.46 6 months after treatment (P < 0,01). Oxidative stress parameters showed slight modifications over t he time period studied, but the differences were not significant except for a decrease in thiobarbituric acid-reactive products 6 months after therapy (P < 0.05) and in serum uric acid concentration 1 and 6 months after thera py (P < 0,01), This report demonstrates slight but significant and persiste nt DNA damage in I-131-treated patients as assessed by cytogenetic assays. There was no clear correlation between the cytogenetic findings and oxidati ve stress parameters studied.