Cytogenetic Damage in the Peripheral Blood Lymphocytes of Thyroid Cancer Patients during Pre and Post 131I Therapy

Abstract

Aim: 131 I therapy is widely used in patients of differentiated thyroid carcinoma for the ablation of remnant thyroid tissue post thyroidectomy as well as metastasis. These patients are in hypothyroid state with consequent reduction in renal clearance of 131 I thereby increasing the extent of whole body exposure. Present study was carried out to assess the DNA damage due to the presence of thyroid carcinoma as well as posttherapeutic 131 I exposure at 72h by measuring micronuclei (MN) frequency in peripheral blood lymphocytes (PBLs) in patients of differentiated thyroid cancer. Methods: The study group consisted of 25 differentiated thyroid carcinoma patients and 35 healthy donors. The blood samples of the patients were collected pre and post 131 I therapy (1.6-9.3 GBq) and processed for PBL MN frequency by cytokinesis-block MN assay. Results: The mean basal MN frequency was significantly high in thyroid cancer patients as compared to the healthy donors (p< 0.001). 131 I exposed patients demonstrated significant increase in the MN frequency at 72h after therapeutic 131 I exposure compared to their basal MN index ( p<0.001 ). However the percent increase in MN frequency post 131 I therapy did not show any correlation with administered dose in thyroid cancer patients. Conclusion: The study has revealed significant DNA damage in PBLs as indicated by increased PBL MN frequency post 131 I therapy. However marked individual variations were observed in the DNA damage response to 131 I therapy.