Evidence of increased chromosomal abnormalities in French Polynesian thyroid cancer patients
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The aim of this study was to evaluate the frequency of chromosomal abnormalities in thyroid cancer patients before and after radioactive iodine administration in order to assess cytogenetic particularity in Polynesian thyroid cancer patients.
Chromosomal abnormalities were studied in 30 Polynesian patients with differentiated thyroid cancer, prior to and 4 days after 131I administration. Unstable chromosomal abnormalities were counted in peripheral blood lymphocytes using a conventional cytogenetic method. Peripheral blood was irradiated in vitro at different doses (0.5, 1 and 2 Gy) in order to establish the dose-response of the lymphocytes. Control groups were composed of 50 European thyroid cancer patients before and after first administration of 131I, and of ten European healthy donors. In addition, in vitro irradiation assays were performed at different doses (0.5, 1 and 2 Gy).
The relative risk of spontaneous dicentrics before any radiation treatment was 2.9 (95% CI 1.7–5.1) times higher among Polynesian thyroid patients than among European thyroid cancer patients. After in vitro irradiation, the rise in frequency of dicentrics was similar in the Polynesian thyroid cancer group and the European thyroid patients and healthy donors. Four days after administration of 3.7 GBq 131I, the relative risk for a dicentric per cell was 1.3 (95% CI 1.0–1.5) times higher in Polynesian than in European patients. This can be explained by higher 131I retention in Polynesian compared with European patients. The results obtained revealed an increased frequency of cytogenetic abnormalities in Polynesian thyroid cancer patients compared with European control patients.
These preliminary findings are compatible with possible previous environmental aggression and therefore imply a need for further investigations on larger series including, in particular, French Polynesian healthy donors. In addition to French Polynesians, Maori and Hawaiian control groups could be useful.
KeywordsPolynesian Thyroid cancer Chromosomal abnormalities Dicentrics Biological dosimetry
This work was funded by grants from Electricité de France (EDF) 98-04 and Institut Gustave Roussy CCR# 98-25. The authors thank the nurses, technologists and secretaries for their support and participation in this study. We are grateful to Prof. Martin Schlumberger (Department of Nuclear Medicine) for clinical data and to Nadine Béron-Gaillard for her efficient collaboration. We are indebted to Mrs. Corinne Ridgway for reviewing the manuscript.
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