title: Cytogenetic and dosimetric effects of (131)I in patients with differentiated thyroid carcinoma: comparison between stimulation with rhTSH and thyroid hormone withdrawal treatments.
abstract: A study directed to the cytogenetic and dosimetric aspects of radionuclides of medical interest is very valuable, both for an accurate evaluation of the dose received by the patients, and consequently of the genetic damage, and for the optimization of therapeutic strategies. Cytogenetic and dosimetric effects of (131)I in lymphocytes of thyroidectomized differentiated thyroid cancer (DTC) patients were evaluated through chromosome aberration (CA) technique: Euthyroid patients submitted to recombinant human thyroid-stimulating hormone (rhTSH) therapy (group A) were compared with hypothyroid patients left without levothyroxine treatment (group B). CA analysis was carried out prior to and 24 h, 1 week, 1 month and 1 year after radioiodine administration (4995-7030 MBq) in both groups. An activity-response curve of (131)I (0.074-0.740 MBq/mL) was elaborated, comparing dicentric chromosomes in vivo and in vitro in order to estimate the absorbed dose through Monte Carlo simulations. In general, radioiodine therapy induced a higher total CA rate in hypothyroid patients as compared to euthyroid patients. The frequencies of dicentrics obtained in DTC patients 24 h after treatment were equivalent to those induced in vitro (0.2903 ± 0.1005 MBq/mL in group A and 0.2391 ± 0.1019 MBq/mL in group B), corresponding to absorbed doses of 0.65 ± 0.23 Gy and 0.53 ± 0.23 Gy, respectively. The effect on lymphocytes of internal radiation induced by (131)I therapy is minimal when based on the frequencies of CA 1 year after the treatment, maintaining a higher quality of life for DTC patients receiving rhTSH-aided therapy.
authors.affiliation: Centro de Biotecnologia, Instituto de Pesquisas Energéticas e Nucleares (IPEN), Comissão Nacional de Energia Nuclear (CNEN), IPEN-CNEN/SP, Caixa Postal 11049, Av. Prof. Lineu Prestes, 2242, Cidade Universitária, São Paulo, CEP 05508-900, Brazil.
authors.forename: Márcia Augusta
authors.initials: MA
authors.lastname: da Silva
authors.affiliation: Centro de Biotecnologia, Instituto de Pesquisas Energéticas e Nucleares (IPEN), Comissão Nacional de Energia Nuclear (CNEN), IPEN-CNEN/SP, Caixa Postal 11049, Av. Prof. Lineu Prestes, 2242, Cidade Universitária, São Paulo, CEP 05508-900, Brazil.
authors.forename: Flávia Gomes Silva
authors.initials: FG
authors.lastname: Valgôde
authors.affiliation: Centro de Medicina Nuclear, Faculdade de Medicina da Universidade de São Paulo, Rua Ouvídio Pires de Campos, s/n, São Paulo, Brazil.
authors.forename: Júlia Armiliato
authors.initials: JA
authors.lastname: Gonzalez
authors.affiliation: Centro de Engenharia Nuclear, Instituto de Pesquisas Energéticas e Nucleares, IPEN-CNEN/SP, Caixa Postal 11049, Av. Prof. Lineu Prestes, 2242, Cidade Universitária, São Paulo, CEP 05508-900, Brazil.
authors.forename: Hélio
authors.initials: H
authors.lastname: Yoriyaz
authors.affiliation: Centro de Medicina Nuclear, Faculdade de Medicina da Universidade de São Paulo, Rua Ouvídio Pires de Campos, s/n, São Paulo, Brazil.
authors.forename: Maria Inês Calil Cury
authors.initials: MI
authors.lastname: Guimarães
authors.affiliation: Centro de Biotecnologia, Instituto de Pesquisas Energéticas e Nucleares (IPEN), Comissão Nacional de Energia Nuclear (CNEN), IPEN-CNEN/SP, Caixa Postal 11049, Av. Prof. Lineu Prestes, 2242, Cidade Universitária, São Paulo, CEP 05508-900, Brazil.
authors.forename: Maria Teresa Carvalho Pinto
authors.initials: MT
authors.lastname: Ribela
authors.affiliation: Centro de Medicina Nuclear, Faculdade de Medicina da Universidade de São Paulo, Rua Ouvídio Pires de Campos, s/n, São Paulo, Brazil.
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Buchpiguel
authors.affiliation: Centro de Biotecnologia, Instituto de Pesquisas Energéticas e Nucleares (IPEN), Comissão Nacional de Energia Nuclear (CNEN), IPEN-CNEN/SP, Caixa Postal 11049, Av. Prof. Lineu Prestes, 2242, Cidade Universitária, São Paulo, CEP 05508-900, Brazil.
authors.forename: Paolo
authors.initials: P
authors.lastname: Bartolini
authors.affiliation: Centro de Biotecnologia, Instituto de Pesquisas Energéticas e Nucleares (IPEN), Comissão Nacional de Energia Nuclear (CNEN), IPEN-CNEN/SP, Caixa Postal 11049, Av. Prof. Lineu Prestes, 2242, Cidade Universitária, São Paulo, CEP 05508-900, Brazil. kokazaki@ipen.br.
authors.forename: Kayo
authors.initials: K
authors.lastname: Okazaki
mesh_terms: D000328:Adult; D002869:Chromosome Aberrations; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000627:therapeutic use / Q000633:toxicity; D008214:Lymphocytes / Q000378:metabolism / Q000528:radiation effects; D008875:Middle Aged; D011829:Radiation Dosage; D013964:Thyroid Neoplasms / Q000188:drug therapy*; D057073:Thyrotropin Alfa / Q000494:pharmacology; D013974:Thyroxine / Q000627:therapeutic use
chemical_list: D007457:Iodine Radioisotopes; D057073:Thyrotropin Alfa; D013974:Thyroxine
keywords: 131I; Biological dosimetry; Chromosome aberration; Differentiated thyroid carcinoma; Recombinant human thyroid-stimulating hormone; Thyroid hormone withdrawal