Cytogenetic effect due to 131I in patients with differentiated thyroid cancer: comparison between recombinant human thyrotropin (r-hTSH) administration and therapy based on thyroid hormone suspension

Abstract

The effects of internal irradiation caused by radiopharmaceuticals being utilized in nuclear medicine are very little studied at the cellular levels. A study directed to the cytogenetic and dosimetric aspects of radionuclides of medical interest is thus very valuable, either for an accurate evaluation of the dose received by the patient and of the consequent genetical damage, or for the optimization of the methodologies being developed according to the national and international scenario. In the present study acute and late cytogenetic effects due to 131I ablation will be analyzed in patients with differentiated thyroid cancer through the chromosomic aberration technique. The possible chromosomic damages induced in euthyroid patients submitted to r-hTSH (Thyrogen) therapy will be compared to those induced in patients maintained in hypothyroid condition through prolonged suspension of thyroid hormone (L-T4) administration. The chromosomic analysis will be carried out before, 24h, one week, one month and one year after radioiodine administration (3700 MBq). The determination of 131I excretion levels and dosimetric studies directed to estimate the whole body and blood absorbed dose will be carried out in the two groups of patients. At the same time in vitro assays based on the construction of dose-response curves for chromosomic damage due to different radioactive concentrations of 131I (0.74 to 2.22 MBq/mL) will be compared to those obtained in vivo in the two patients groups, in order to confirm and establish the dose-response curves. (AU)