Abstract

NAVARRO FERNANDEZ, J. et al. Actividad genotóxica de la terapia con I¹³¹ en pacientes tratados por carcinomas de tiroides. Oncología (Barc.) [online]. 2004, vol.27, n.1, pp.40-48. ISSN 0378-4835.

INTRODUCTION: The micronuclei (MN) test of irradiated human lymphocytes with cytogenetic arrest (LCA) is employed to evaluate the chromosomal damage and the genotoxic effect of different physical and chemical agents. OBJECTIVE: To determine the possible genotoxic effect induced by I¹³¹ therapy of thyroid cancer patients, and to calculate the equivalent total body irradiation (TBI) of the treatment. MATERIAL AND METHODS: The frequency of appearance of MN was determined in LCA cultures from three different groups: 1) 35 healthy volunteers, in order to establish the spontaneous frequency of MN; 2) 9 supposedly healthy volunteers to carry out in vitro dose-response curves of gamma rays irradiated lymphocytes, and 3) 25 patients with thyroid carcinoma that had received ablative doses of I131 to treat the disease. The number of MN per 500 LCB before the treatment and three days after the administration of I¹³¹ was determined. The equivalent TBI of the therapy was assessed by comparing the frequency of MN in lymphocytes obtained three days after the I¹³¹ administration with the dose of gamma radiation necessary to produce the same frequency of MN in in vitro irradiated lymphocytes from healthy people. RESULTS: A lineal relationship was found between the frequency of MN and the dose of gamma radiation in vitro. The MN frequency of the lymphocytes after the I¹³¹ treatment was 8.89 MN per 500 LCA, a significantly higher figure doubling the spontaneous basal frequency of 4.08 MN per 500 LCA (p<0.01). CONCLUSION: The I¹³¹ therapy induces a significant increase of chromosomal damage of the lymphocytes from thyroid cancer patients receiving I¹³¹ radiation, that has an equivalent TBI of 13 cGy during the first three days of treatment.

Keywords : Radiation effects; Lymphocytes; Micronuclei; Thyroid cancer.

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