Twenty years' experience with post-Chernobyl thyroid cancer.

Strangeways Research Laboratory, Worts Causeway, Cambridge CB1 8RN, UK.
Best Practice & Research: Clinical Endocrinology & Metabolism (Impact Factor: 4.91). 01/2009; 22(6):1061-73. DOI: 10.1016/j.beem.2008.09.020
Source: PubMed

ABSTRACT Chernobyl, the largest ever nuclear accident, caused a huge release of radioactive isotopes, including nearly 2x10(18) Bq of iodine-131. Four years later an increase in thyroid cancer incidence, virtually all papillary carcinomas in children, occurred in the highly exposed areas. The increase has continued, and with increasing latency the tumour molecular and morphological pathology has changed; further changes may occur in the future. Children under the age of 1 at exposure show the highest susceptibility, and carry this risk with them into adult life; 4000 cases have been attributed to the accident, but so far very few have died. The risk falls rapidly with increasing age at exposure; it is doubtful if there is any risk for adults at exposure. Other factors linked to susceptibility to thyroid carcinogenesis after Chernobyl include dose, iodine deficiency, and genetic factors. Other consequences are briefly covered.

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    ABSTRACT: BACKGROUND: Recent studies of children and adolescents who were exposed to radioactive iodine-131 (I-131) after the 1986 Chernobyl nuclear accident in Ukraine exhibited a significant dose-related increase in the risk of thyroid cancer, but the association of radiation doses with tumor histologic and morphologic features is not clear. METHODS: A cohort of 11,664 individuals in Belarus who were aged ≤18 years at the time of the accident underwent 3 cycles of thyroid screening during 1997 to 2008. I-131 thyroid doses were estimated from individual thyroid activity measurements taken within 2 months after the accident and from dosimetric questionnaire data. Demographic, clinical, and tumor pathologic characteristics of the patients with thyroid cancer were analyzed using 1-way analysis of variance, chi-square tests or Fisher exact tests, and logistic regression. RESULTS: In total, 158 thyroid cancers were identified as a result of screening. The majority of patients had T1a and T1b tumors (93.7%), with many positive regional lymph nodes (N1; 60.6%) but few distant metastases (M1; <1%). Higher I-131 doses were associated with higher frequency of solid and diffuse sclerosing variants of thyroid cancer (P <.01) and histologic features of cancer aggressiveness, such as lymphatic vessel invasion, intra- thyroidal infiltration, and multifocality (all P <.03). Latency was not correlated with radiation dose. Fifty-two patients with self- reported thyroid cancers which were diagnosed before 1997 were younger at the time of the accident and had a higher percentage of solid variant cancers compared with patients who had screening-detected thyroid cancers (all P <.0001). CONCLUSIONS: I-131 thyroid radiation doses were associated with a significantly greater frequency of solid and diffuse sclerosing variants of thyroid cancer and various features of tumor aggressiveness.
    Cancer 02/2015; 121(3):457-466. DOI:10.1002/cncr.29073 · 4.90 Impact Factor
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    ABSTRACT: Background Radioiodine is routinely used or proposed for diagnostic and therapeutic purposes: 123I, 125I and 131I for diagnostics and 125I and 131I for therapy. When radioiodine-labelled pharmaceuticals are administered to the body, radioiodide might be released into the circulation and taken up by the thyroid gland, which may then be an organ at risk. The aim of this study was to compare dosimetric properties for 123I, 125I and 131I in previously developed thyroid models for man, rat and mouse. Methods Dosimetric calculations were performed using the Monte Carlo code MCNPX 2.6.0 and nuclear decay data from ICRP 107. Only the non-radiative transitions in the decays were considered. The S value was determined for the cell nuclei in species-specific thyroid follicle models for mouse, rat and man for different spatial distributions of radioiodine. Results For the species-specific single follicle models with radioiodine homogeneously within the follicle lumen, the highest S value came from 131I, with the largest contribution from the β particles. When radioiodine was homogeneously distributed within the follicle cells or the follicle cell nucleus, the highest contribution originated from 125I, about two times higher than 123I, with the largest contribution from the Auger electrons. The mean absorbed dose calculated for our human thyroid multiple follicle model, assuming homogenous distribution of for 123I, 125I, or 131I within the follicle lumens and follicle cells, was 9%, 18% and 4% higher, respectively, compared with the mean absorbed dose according to Medical Internal Radiation Dose (MIRD) formalism and nuclear decay data. When radioiodine was homogeneously distributed in the follicle lumens, our calculations gave up to 90% lower mean absorbed dose for 125I compared to MIRD (20% lower for 123I, and 2% lower for 131I). Conclusions This study clearly demonstrates the importance of using more detailed dosimetric methods and models than MIRD formalism for radioiodine, especially 123I and 125I, in the thyroid. For radioiodine homogeneously distributed in the follicle lumens our calculations for the human multiple follicle models gave up to 90% lower mean absorbed dose compared with MIRD formalism.
    06/2014; 4:23. DOI:10.1186/s13550-014-0023-9
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    ABSTRACT: With improvements in the survival rates after childhood cancer, many clinicians have turned their attention to reporting on late effects, and how they might be prevented or treated. In childhood the thyroid gland is especially vulnerable to the carcinogenic action of ionizing radiation. This retrospective study focused on secondary thyroid cancers seen at our institution over more than 30 years (between 1980 and 2012) in patients treated for other malignancies in pediatric age. 36 patients were identified. In most cases, the primary cancer had been Hodgkin disease, and all the patients had been administered radiotherapy for their first malignancy. The secondary thyroid cancers were treated with total thyroidectomy in 27 cases (six with lymphadenectomy), and hemithyroidectomy in nine (one with lymphadenectomy). 12 Patients were also given radiometabolic therapy. All but two had TSH suppression therapy. The histological diagnoses were: 31 papillary and five follicular carcinomas. At 5 and 10 years, the OS was 100 and 95 %, respectively, and the PFS was 96 and 83 %. None of the patients died of their thyroid disease. Nodal involvement at onset was the only factor correlating with recurrence. Surgical sequelae only occurred in patients who underwent total thyroidectomy. Survival in these patients did not depend on the extent of surgery on the thyroid parenchyma. Our data confirm a good prognosis for secondary thyroid cancer, prompting us to encourage a minimalist approach to the treatment of these particular patients wherever possible.
    Medical Oncology 08/2014; 31(8):121. DOI:10.1007/s12032-014-0121-6 · 2.06 Impact Factor


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