Feasibility Study Shows Multicenter, Observational Case-Control Study Is Practicable to Determine Risk of Secondary Breast Cancer in Females With Differentiated Thyroid Carcinoma Given Radioiodine Therapy in Their Childhood or Adolescence; Findings Also Suggest Possible Fertility Impairment in Such Patients

Objective: This single-center, observational case-control feasibility study sought to test key elements of a protocol for an eventual long-term international observational case-control study of a larger patient cohort, to evaluate the risk of breast cancer as a second primary malignancy in females with differentiated thyroid cancer (DTC) given radioiodine therapy (RAI) during childhood or adolescence. Patients: Females developing DTC after the Chernobyl accident in Belarus and ≤19 years old at the time of thyroid surgery were enrolled: patients given RAI (n = 111) and controls of similar age not given RAI (n = 90). Results: One case of breast cancer was newly diagnosed among the RAI patients, but none in controls. Patients given RAI significantly less frequently needed 2^nd surgeries than did controls (23%, 26/111 vs. 39%, 35/90, P < 0.05); the main indication for such procedures usually is suspicion of local recurrence. RAI patients appeared to have had more frequent reproductive difficulties than did controls: 78% (87/111) of the former vs. 93% (84/90) of the latter had a history of pregnancy (P < 0.01), and the mean number of pregnancies was 1.5 ± 1.2 in RAI patients vs. 1.9±1.1 in controls (P < 0.05). Most notably, infertility was observed in 23% (26/111) of RAI patients vs. 4% (4/90) of controls (P < 0.01). In conclusion, a international observational case-control study on breast cancer after DTC in patients given RAI vs. not given RAI appears to be feasible. Additional research and everyday clinical attention should be devoted to reproductive function after RAI in young females.

DNA damage evaluated by alkaline single cell gel electrophoresis (SCGE) in children of Chernobyl, 10 years after the disaster

Using the alkaline single cell gel electrophoresis (Comet) assay, the extent of DNA damage was evaluated in leukocytes of 43 Belarussian children (16 healthy and 27 affected by thyroid cancer). Thirty-nine healthy children from Pisa (Italy) were enrolled in the study as controls. In addition to basal levels of DNA damage, leukocytes were treated in vitro with bleomycin (BLM), a radiomimetic drug, to evaluate a possible adaptive response in different groups of children. Results with the Comet assay indicated an increased level of DNA damage (P=0.037) in leukocytes of Belarussian children compared to the Italian control group. In addition, within the Belarus group, lower basal levels of DNA damage (P<0.001) were found in children with cancer compared to healthy children. Tumor affected children were living in less radiocontaminated areas (P<0.04) than the healthy children and there was a significant relationship (P=0.03) between the amount of environmental radiocontamination and DNA damage in leukocytes. There were no differences in the sensitivity of leukocytes from different groups of children to BLM, indicating the absence of an adaptive response. The lack of an adaptive response may have been due to the use of noncycling cells and/or the bleomycin dose chosen. Tests for the presence of clastogenic factors (CF) in the blood serum of children showed that 39% of the tumor affected children and 19% of the healthy children in the exposed group were positive as compared to the Italian control group (0%) (Chi-square test, P<0.04). The higher levels of genomic damage in children evaluated 10 years after the Chernobyl disaster could be related to the increased incidence of individuals with CF.

Micronucleus frequency in Gomel (Belarus) children affected and not affected by thyroid cancer

Cytogenetic monitoring was carried out on a group of children from Gomel (Belarus), one of the areas most severely affected by radioactive contamination following the accident at the Chernobyl nuclear power plant, in 1986. We performed the micronucleus test (MN) in binucleated lymphocytes of 42 children (mean age: 11+/-2.34 years), 16 of whom were affected by thyroid gland tumor. Thirty healthy children living in Pisa (mean age: 14.96+/-2.17 years) were enrolled in the study as controls. Thyroid tumor affected children living in Gomel showed a statistically significant increase in the frequency of micronucleated cells as compared with the healthy children from Pisa. Moreover, a significant correlation was found between MN frequency and both the presence of tumor and higher 137Cs contamination. In addition, higher 137Cs contamination was more frequently observed in tumor affected children. These results suggest that the increased MN frequency is attributable more to 137Cs contamination rather than to the presence of the tumor itself.

Cytogenetic damage in lymphocytes of healthy and thyroid tumor-affected children from the Gomel region (Belarus)

During 1994, 19 thyroid tumor-affected children and 17 healthy children from the Gomel region, one of the areas most polluted by the Chernobyl fallout, were analysed for (i) the presence of in their urine and (ii) chromosome aberrations (CA) in circulating lymphocytes. They were compared with 35 healthy children from Pisa, Italy. Tumor-affected children showed significantly (p<0.05) higher levels in their urine as compared to healthy controls from the Gomel region. No radioactivity was found in urine from the Pisa controls. CA frequency was significantly higher in tumor-affected children compared to the Gomel controls, but was not significantly different between Gomel and Pisa controls. However, dicentric chromosomes were found in a significantly (p<0.01) greater proportion in both affected and healthy Gomel children (3.4 and 1.3/1000 cells, respectively) as compared to the Pisa controls (0.4/1000 cells). Multiple regression analysis showed that the proportion of cells with acentric fragments, dicentric and ring chromosomes was significantly correlated (p<0.05) with the amount of excreted in their urine. These findings suggest that children from the Gomel region were still being exposed to radionuclides, which makes it possible to study a dose-effect relationship.

Comet assay on children's leukocytes 8 years after the Chernobyl disaster

DNA damage, mainly single strand breaks, was evaluated by single cell gel electrophoresis, in leukocytes of 36 healthy and 14 thyroid cancer-affected children prior to radio-therapy. The children come from the Gomel region, one of the areas most heavily radio-contaminated by the Chernobyl fallout. In addition, leukocytes were treated with a challenge dose of bleomycin (BLM, 1.5 micrograms/ml), to assess the presence of an adaptive response (AR) potentially resulting from chronic exposure to radionuclides. As controls, 13 children living in Pisa (Italy) were enrolled in the study. Children with thyroid cancer show higher (p < 0.001) DNA damage than healthy ones. No difference was found between healthy children from Gomel and from Pisa. A reduction in the response to BLM was significantly linked to low plasma levels of FT4 hormone (p < 0.0001), to the presence of the tumor (p < 0.002), to being female (p < 0.02), and to a higher 137Cs body burden (p < 0.03).

FISH analysis of translocations in lymphocytes of children exposed to the Chernobyl fallout: preferential involvement of chromosome 10

Using whole-chromosome painting probes, we have analyzed the frequency of translocations of chromosomes 1, 3, and 10 in peripheral lymphocytes of 20 Gomel (Belarus) children, including both thyroid tumor affected and healthy individuals. Gomel was one of the most heavily radiocontaminated areas due to fallout from the Chernobyl nuclear power plant disaster. As controls, 14 healthy children from Pisa (Italy) were investigated simultaneously. Translocation rates were significantly higher in the tumor affected (1.71 +/- 0.68) and healthy Gomel children (2.69 +/- 0.50) than in the Italian controls (0.79 +/- 0.24). We also observed, in healthy Gomel children, an approximately three-fold higher frequency of chromosome 10 translocations compared to translocations affecting chromosomes 1 or 3 (P = 0.0096), a difference that was made even larger (about four fold) after correcting for chromosome size (P = 0.0009). This finding suggests a preferential involvement of chromosome 10 in translocations induced in vivo by low levels of ionizing radiation.

Epidemiologic and clinical evaluation of thyroid cancer in children from the Gomel region (Belarus)

This study reviews the epidemiology of thyroid cancer during childhood from the environs of Gomel in Belarus and the clinical data of 64 children aged 4 to 16 years from this area who had been diagnosed with differentiated thyroid carcinoma following the nuclear accident of Chernobyl. One case of thyroid cancer in children (aged < 15 years at diagnosis) was observed during the period 1981-1985 (rate = 0.5; expressed as annual averages per million children under age 15 years in the region of Gomel and period identified) before the Chernobyl accident. Twenty-one cases of thyroid cancer in children were observed during 1986-1990 (rate = 10.5) and 143 (rate 97) during 1991-1994 after the Chernobyl accident. During the first 7 months of 1995, there were 33 more cases of thyroid cancer observed in children. Three children with thyroid cancer were born since 1986 in the Gomel region. A total of 64 children aged 4 to 16 years from this area who had been diagnosed with differentiated thyroid carcinoma had been reviewed by us during the period May to November 1994. The female/male ratio was 1.4:1.0. At the time of the first diagnosis the mean age of the children was 9.4 +/- 2.8 years, and at the time of the accident their mean age was 3.8 +/- 2.4 years. More than 90% of the patients were less than 6 years of age and 3 were still in utero at the time of the accident. The period of latency between the accident and the first diagnosis was 5.6 +/- 1.5 years. Their ages at the time of the first diagnosis and their ages at the time of the accident were significantly correlated (p = 0.001); there was no significant correlation between the age of each child at the time of the accident and the latent period before the onset of carcinoma. The aggressiveness of the tumor, evaluated on the basis of T stage, lymph node status, and lung metastases, did not correlate with age at the time of the first diagnosis or with the age at the time of the accident. The susceptibility of the thyroid to the carcinogenetic effects of radiation, particularly during the first years of life (< 5 years) has clearly been demonstrated. However, there appears to be no correlation between the aggressiveness of the tumor and the age of the patients.