Structural chromosomal aberrations before and after administration of 20 muCi iodine-131

Comparison of Chromosome Aberration Frequency before and after Administration of 131I in Two Groups of Thyroid Cancer Patients

The chromosome aberration frequencies of 10 thyroid cancer patients, before and after their first radioiodine treatment (group A), were compared to the frequencies found in another 10 subjects previously treated with two or more radioiodine administrations (group B). Our data show that the relative increase in chromosome-type aberrations was similar in the two groups: from 2.0% to 3.7% (group A) and from 4.7% to 9.0% (group B). However, the increase in the number of cells with aberrations was greater in group A. Moreover, the higher frequency of aberrations in group B, even before the radioiodine treatment, points out the effect of previous treatments and demonstrates the persistence of this type of lesion. The sister chromatid exchange frequency in the two groups was also analysed, but no effect bound to the radioiodine treatment could be demonstrated.

A cytogenetic follow-up study of thyroid cancer patients treated with 131I

To determine the genotoxic risk associated with therapeutic exposure to 131I, we studied the presence of micronuclei (MN) in binucleated peripheral blood lymphocytes of a group of 22 women, patients of thyroid cancer, who received 131I sodium iodide orally as an adjuvant after total thyroidectomy. The cytogenetic study was conducted following annual check-up, the patients having received the therapeutic dose between 1 and 5 years before the study. The results show that there are no significant differences in MN frequency between the patients and the control group, the latter composed of 19 unexposed women. These findings could indicate that any possible genetic damage induced by therapeutic exposure to 131I is eliminated after a period of 1 year.

Chromosome aberrations in Norwegian reindeer following the Chernobyl accident

Chromosome analyses were carried out on peripheral blood lymphocytes of semi-domestic reindeer in Norway which had been exposed to varying amounts of radiocesium emanating from the Chernobyl accident. The sampling was done in the period 1987-1990. The material included 192 reindeer, originating from four herds in central Norway, an area considerably affected by fallout from the Chernobyl accident, and from three herds in northern Norway which was unaffected by fallout from the accident. Significant heterogeneity in the distribution of chromosome aberrations between herds was observed. The pattern of chromosome aberration frequencies between herds was not related to the variation in radiocesium exposure from the Chernobyl accident. Other factors than the Chernobyl accident appear therefore to be of importance for the distribution of aberration frequencies found among present herds. Within the most contaminated area the reindeer born in 1986 showed significantly more chromosome aberrations than those born both before and after 1986. This could suggest that the Chernobyl accident fallout created an effect particularly among calves, during the immediate post-accident period in the most exposed areas.