Tratamento do carcinoma diferenciado da tireóide com iodo-131: intervenções para aumentar a dose absorvida de radiação

Abstract

RESUMOObjetivo: Analisar medidas tomadas para aumentar a dose de radiação absorvida (DOSE) durante o tratamento do carcinoma diferenciado da tireóide (CDT) com iodo-131. Métodos: As abordagens para aumentar a DOSE na radioiodoterapia são: redução da competição com iodo não-radioativo, estímulo da captação/retenção celular e aumento da atividade administrada. Revisaram-se os fundamentos e resultados de cada um destes métodos. Resultados: Apesar de ser difícil confirmar aumento de sobrevida, existe relação direta entre a DOSE e a resposta no CDT. Diferentes abordagens permitem o aumento da DOSE nos tecidos, inferindo-se uma possível melhora na resposta dos tumores ao tratamento com iodo-131. Apesar do prognóstico relativamente benigno da doença, a melhoria da resposta é importante nos casos de alto risco, em que as alternativas de tratamento são limitadas. Conclusões: As intervenções descritas permitem aumentar a DOSE durante o tratamento do CDT, podendo ser empregadas para casos de alto risco. Our aim was to analyze measures taken to increase the radiation absorbed dose (DOSE) during treatment of well-differentiated thyroid cancer (DTC) with iodine-131. Methods: An increase in DOSE is achieved by: avoiding competition with non-radioactive iodine, stimulating cellular uptake/retention, increasing the administered activity. Basis and results of each one of these methods were reviewed. Results: Although it is difficult to demonstrate an increase in survival, there is a direct relation between DOSE and tumoral response in DTC. Different approaches can be used aiming an increase in DOSE, with a possible improvement in tumoral response for treatment with iodine-131. Although DTC is a relatively benign disease, a better response to treatment is highly desirable in high-risk patients, who have few other options of therapy. Conclusions: An increase in DOSE during treatment of DTC can be achieved using the described interventions, which should be used in high-risk cases of DTC.

Low iodine diet does not improve the efficacy of radioiodine for the treatment of Graves’ disease

“…This enhanced uptake might result from increased NIS gene expression, a higher specific activity of 131 I or the increased sensitivity of the remaining thyroid tissue to TSH (19,20). Despite the controversy regarding the appropriate degree and duration of a LID (26,27), the general recommendation is that patients should consume a LID, generally consisting of less than 50 μg iodine/day, for 1 to 4 weeks (18,22). This stringent diet results in a significant decrease in urinary iodine excretion, ranging from 50% to 80%; more than 80% of the patients develop iodine deficiency.…”

“…Two weeks before RAIT, the patients were allocated alternately into 2 groups: one group consumed a LID (n = 31), corresponding to a maximum amount of 50 µg iodine/day (22), and the other group (n = 36) was instructed to maintain a regular diet (RD). We monitored patient compliance to their diet each week and emphasized its importance.…”

Mutagenicity of diagnostic and therapeutical doses of radiopharmaceutical iodine-131 in Wistar rats

“…These products can perpetuate and further increase chromosomal damage and may eventually exceed the DNA repair capacity (Ballardin et al 2002). Despite not being the most irradiated location, bone marrow is the critical target in determining the maximum dose of 131 I to be administered due to its high radiosensitivity (Sapienza et al 2005), which enables the use of the test system used here. In this study, the estimated radiation dose that the bone marrow of rats received from 131 I was 0.001-0.003 cGy for the concentration of 5 lCi, 0.007-0.016 cGy for 25 lCi, 0.015-0.032 cGy for 50 lCi and 0.078-0.164 cGy for 250 lCi (calculated data, extrapolated from the work of Ballardin et al (2002)).…”

Efeitos citogenético e dosimétrico do 131I em pacientes com câncer diferenciado da tireóide com e sem estimulação com r-hTSH. Estudo em células tumorais tireoidianas (WRO) tratadas com 131I e 60Co in vitro

“…(1) minimamente invasivo ou capsulado e (2) amplamente invasivo. Existe pouca sobreposição entre os dois tipos (Melmed et al, 2011 No primeiro regime de tratamento, o paciente interrompe a ingestão dos hormônios T 4 (4 a 6 semanas) e/ou T 3 (2 a 3 semanas) para que as células tireoidianas realizem a máxima captação de iodo (Sapienza et al, 2005;Tuttle, 2008). Porém, este procedimento acarreta o estado hipotireoideo nos pacientes, causando reações adversas como fadiga, depressão, distúrbio do sono, inabilidade para executar atividades diárias normais, resultando numa queda na qualidade de vida e causando uma inabilidade temporária para o trabalho (Borget et al, 2007).…”