The alkaline single-cell gel electrophoresis (SCGE) assay applied to the analysis of radiation-induced DNA damage in thyroid cancer patients treated with 131I

The alkaline single-cell gel electrophoresis (SCGE or Comet) assay appears to be a promising tool for measuring DNA damage at the individual cell level in both in vitro and in vivo studies. To provide further data on the possible applicability of this assay in human biomonitoring studies, we have evaluated the eventual genetic damage induced by therapeutic exposure to I-131, by measuring the Comet length and the amount of DNA damage in peripheral blood leukocytes from a group of 28 thyroid cancer patients who received I-131 sodium iodide via oral administration. Blood samples were taken just before the treatment and 1 week after it. From the results obtained after radioiodine therapy, a small increase in the Comet length and in the grade of DNA damage is observed; however, this increase is not statistically significant because of inter-individual variability and the variable responses before and after I-131 treatment. Considering our previous studies showing significant increases in the frequency of cytogenetic damage (when measured as micronuclei) in patients treated with relatively low doses of I-131, the results obtained in the present work by using the Comet assay could indicate that 1 week after the exposure most of the radioiodine-induced DNA lesions, that can be detected with this assay, have already been repaired. (C) 1998 Elsevier Science B,V.