RESUMO
CONTEXT: Thyroid cancer is the most common endocrine malignancy worldwide. Iodine-131 is used in the treatment of thyroid cancer with dosage of 100 mCi. In the medical applications of ionizing radiation besides the advantages such as diagnosis and treatment of diseases, the risks arising from exposure should be considered as well. AIMS: The present study aimed to evaluate the changes in expression levels of apoptotic Bax and Bcl-2 and the ratio of Bax/Bcl-2, in the peripheral blood lymphocytes (PBLs) of patients with differentiated thyroid cancer (DTC). SETTINGS AND DESIGN: This study was conducted on fifty thyroid cancer patients who had undergone surgery and were under treatment with 100 and 150 mCi doses. Subjects and Methods: Blood samples were taken from the patients, one before iodine treatment and another 48 h after therapy. Bax and Bcl-2 gene expression levels were measured by using real-time reverse transcriptase polymerase chain reaction. STATISTICAL ANALYSIS USED: The data were analyzed using one-way analysis of variance followed by samples t-test and independent samples t-test. RESULTS: Significant changes were observed in the percentage of apoptotic cells, in groups, after radioiodine therapy compared with before treatment. The ratio of Bax/Bcl-2 in both groups showed a significant increase (P < 0.001). The relative expression level of Bax gene showed a significant increase in comparison with the control group. CONCLUSIONS: Iodine therapy reduced expression of Bcl-2 and a significant expression of Bax and finally increased the ratio of Bax/Bcl-2. Iodine therapy led to apoptosis in the PBLs of patients with DTC. Therefore, it can be suggested that this method can be useful for monitoring and detecting destructive effects of ionizing radiation in nuclear medicine patients.
