title: Cytogenetic damage after 131-iodine treatment for hyperthyroidism and thyroid cancer. A study using the micronucleus test.
abstract: To detect the incidence and persistence of potential chromosome damage induced by iodine-131 therapy, we applied the cytokinesis-block micronucleus assay to peripheral blood lymphocytes from hyperthyroidism and thyroid cancer patients treated with 131I. Two groups of patients were evaluated in a longitudinal study; one group was composed of 47 hyperthyroid patients and the other of 39 thyroid cancer patients. In the hyperthyroidism group, the micronuclei frequency was determined before 131I therapy and 1 week, 1 month and 3 months after it. Furthermore, an additional sample was taken from a subgroup of 17 hyperthyroidism patients 6 months after treatment. In the thyroid cancer group, the analysis was also conducted over time, and four samples were studied: before treatment and 1 week, 6 months and 1 year later. Simultaneously, a cross-sectional study was performed with 70 control subjects and 54 thyroid cancer patients who had received the last therapeutic dose 1-6 years before the present study. In the hyperthyroidism group a significant increase in the micronuclei average was found over time. In the sample obtained 6 months after therapy, the micronuclei mean frequency was practically the same as in the sample taken 3 months before. In the thyroid cancer group a twofold increase in the frequency of micronuclei was seen 1 week after therapy. Although this value decreased across time, the micronuclei frequency obtained 1 year after 131I therapy remained higher than the value found before it. Concerning the data from the cross-sectional study, a significant increase in the frequency of micronuclei was detected in the subgroup of thyroid cancer patients treated between 1 and 3 years before the current study. These results indicate that exposure to 131I therapy induces chromosome damage in peripheral lymphocytes and that the cytokinesis-block micronucleus assay is sensitive enough to detect the genetic damage by exposure to sufficiently high levels of radiation from internal radioactive sources.
authors.affiliation: Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain.
authors.forename: S
authors.initials: S
authors.lastname: Gutiérrez
authors.forename: E
authors.initials: E
authors.lastname: Carbonell
authors.forename: P
authors.initials: P
authors.lastname: Galofré
authors.forename: A
authors.initials: A
authors.lastname: Creus
authors.forename: R
authors.initials: R
authors.lastname: Marcos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002869:Chromosome Aberrations; D002877:Chromosomes, Human / Q000528:radiation effects*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D007457:Iodine Radioisotopes / Q000009:adverse effects* / Q000627:therapeutic use; D007963:Leukocytes, Mononuclear / Q000473:pathology / Q000528:radiation effects; D008137:Longitudinal Studies; D008297:Male; D015162:Micronucleus Tests; D008875:Middle Aged; D013964:Thyroid Neoplasms / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*
chemical_list: D007457:Iodine Radioisotopes