Translocation frequencies measured in patients one year after radioactive iodine therapy for thyrotoxicosis.
OBJECTIVE
To investigate the incidence of translocations induced by iodine-131 therapy in thyrotoxicosis patients 1 year after the administration of the radiolabelled compound.


METHODS
Tricolour FISH with whole-chromosome-specific probes for chromosomes 2, 4 and 8 was used for scoring translocations. From the genomic translocation frequencies, derived using the Lucas formula, equivalent whole-body doses were calculated, based on the in vitro (60)Co gamma-ray dose-response curve.


RESULTS
A total of 101 translocations were observed in 4864 metaphases, 63% being of the two-way type. In the control group used for obtaining dose-response data, nine translocations were observed in 5278 metaphases, 55% being two-way translocations. No correlation was found between the observed frequency of translocations and administered radioactivity. Using the in vitro dose-response, an estimated average dose for the group of nine patients of 0.79 +/- 0.22Gy was obtained. Compared with frequencies following the assumption that the involvement of a particular chromosome in a two-break exchange-type aberration is proportional to its DNA content, chromosome 4 was more frequently involved and chromosomes 2 and 8 less frequently involved in chromosomal rearrangements.


CONCLUSIONS
This study shows that (131)I therapy for thyrotoxicosis patients induced translocations, especially in chromosome 4, which could be detected 1 year after the administration of the radiolabelled compound.
Lambert
V
V
Oncology, Radiobiology and Experimental Mutageneticity University of Liège, Liège, Belgium. lambert@ulg.ac.be
Thierens
H
H
Monsieurs
M
M
Roncancio
C
C
Laurent
C
C
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002889:Chromosomes, Human, Pair 2 / Q000235:genetics / Q000528:radiation effects; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics / Q000528:radiation effects; D002898:Chromosomes, Human, Pair 8 / Q000235:genetics / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000009:adverse effects* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D013971:Thyrotoxicosis / Q000235:genetics* / Q000532:radiotherapy*; D013997:Time Factors; D014178:Translocation, Genetic / Q000528:radiation effects*
D007457:Iodine Radioisotopes