Inverse association between age at the time of radiation exposure and extent of disease in cases of radiation-induced childhood thyroid carcinoma in Belarus

Abstract

BACKGROUND Increased incidence of childhood thyroid carcinoma, particularly in the youngest children, has been reported from Belarus since the nuclear reactor accident at Chernobyl in 1986. The relation between disease severity and age at the time of the accident, not previously established in this cohort, was analyzed in this study. METHODS The authors studied the association between disease severity, expressed by TNM classification, and age at radiation exposure in a cohort of 483 patients younger than 8 years at the time of the Chernobyl accident who have been diagnosed with differentiated thyroid carcinoma since 1986 at the Center for Thyroid Cancer in Minsk. The associations between age at radiation exposure and TNM categories were compared among 4 groups of patients who were ages < 2, 2.1–4, 4.1–6, and 6.1–8 years at the time of the accident. Multivariate discriminant analysis was performed to examine the effects of age at the time of the accident, gender, histology, tumor stage, and N classification on the frequency of distant metastasis. RESULTS Younger age at the time of the Chernobyl accident was associated with greater extrathyroidal tumor extension (P < 0.01) and more lymph node involvement (P < 0.0001) and tended to be associated with more distant metastases (P = 0.09). Compared with patients who were ages 6.1–8 years at the time of the accident, patients who were younger than 2 years had significantly more extrathyroidal tumor invasion (P = 0.004), lymph node involvement (P = 0.004), and distant metastases (P = 0.05). The age at diagnosis increased with older age at the time of radiation exposure (linear regression analysis; correlation coefficient = 0.67; P < 0.001). Multivariate analysis revealed that younger age at the time of the accident (P = 0.001) and advanced locoregional tumor extension (P < 0.001) were the only powerful factors influencing the risk for distant metastasis of this malignancy. CONCLUSIONS The severity of disease was associated inversely with age at the time of radiation exposure in these cases of radiation‐induced childhood thyroid carcinoma. Cancer 2000;88:1470–6. © 2000 American Cancer Society.

Thyroid carcinoma after Chernobyl latent period, morphology and aggressiveness

“…The observations on the extent of invasion and the development of peritumour fibrosis support this; the short latency tumours show a higher level of both intra-and extrathyroid invasion than the long latency group, while the long latency group shows a significantly greater development of peritumour fibrosis, usually associated with less-aggressive tumours. In addition, clinical studies showed that tumours with a long latent period were less aggressive (Farahati et al, 2000), although screening could have been relevant, and the study was not controlled for age at exposure. Unfortunately, it was not possible to carry out direct analysis of cells in cycle or of the molecular biology in all of the tumours in our study.…”

Improved radiation protection of the thyroid gland with thyroxine, methimazole, and potassium iodide during diagnostic and therapeutic use of radiolabeled metaiodobenzylguanidine in children with neuroblastoma

“…15 In addition, it is known from animal studies that the risk of developing thyroid carcinoma is increased after long-lasting, elevated thyrotropin concentrations, especially after exposure to radiation. 8 For this reason, although solid evidence in humans is lacking, correcting thyrotropin elevation after exposure to radiation often is advised.…”

“…13,14 Furthermore, thyroid tissue in children appears to be more radiosensitive than in adults, [15][16][17] and children with neuroblastoma may even be more susceptible to radiation effects on this gland compared with children who have other malignancies. 18 To protect the thyroid against these adverse radiation effects, it is common practice to administer excessive amounts of potassium iodide during exposure to radioiodide.…”

Thyroid Cancer Susceptibility and THRA1 and BAT-40 Repeats Polymorphisms

“…X55068). The amplified products were labeled using 2.4 ACi of [a 33 -P]dCTP (Amersham Biosciences, Buckinghamshire, England) and 2.5 units of Taq polymerase were used in the PCR reaction. The BAT-40 primers were 5V-AATAACTTCCTACACCACAAC-3V (4,7,2V,4V,5V,7V -hexachloro-6-carboxyfluorescein-labeled) and 5V-GTAGAGCAA-GACCACCTT-3V (39), which amplify a 126-bp product containing the standard 40 A repeat, according to the sequence of the HSD3B1 gene (Genbank accession no.…”

“…Association studies to identify genetic risk factors to cancer are just emerging (29)(30)(31)(32). Related to thyroid cancer risk, few studies have been reported, mostly referring to environmental factors (33)(34)(35)(36)(37). Consequently, although specific genotypes associated with thyroid cancer risk have not yet been described; as in other common cancers, the importance of genetic variants to the risk of sporadic thyroid cancer might be expected.…”