The Effect of Ginkgo biloba Extract on Genotoxic Damage in Patients with Differentiated Thyroid Carcinoma Receiving Thyroid Remnant Ablation with Iodine-131

Background: Radioiodine (I-131) therapy is usually performed in patients with differentiated thyroid cancer (DTC). Although I-131 is generally considered safe, genotoxic damage has been demonstrated both in vivo and in vitro. The aim of the current study was to evaluate the effect of Ginkgo biloba extract (GBE) on the time-course of appearance, after I-131 therapy for DTC, of plasma factors with chromosome-damaging properties (so-called "clastogenic" factors [CFs]) and of micronuclei (MN) in lymphocytes. Methods: Twenty-three patients (median age 42 years, range 18-73) with DTC receiving I-131 activity (3.7 GBq) for thyroid remnant ablation were randomly assigned to receive GBE (120 mg/day for one month; n = 10) or placebo (n = 13) in a double-blind manner. Blood samples were taken at various intervals (from baseline to 90 days) after I-131 therapy. The frequency of MN in blood lymphocytes was determined, and CFs were assayed in plasma by a method that used MN increase in lymphocytes from an healthy donor as the endpoint of the assay. Results: MN in blood lymphocytes increased significantly after I-131 treatment in the placebo group, peaking at the 7th day (p = 0.002) and slowly declining thereafter. In contrast, in similarly treated patients who were also treated with GBE both before and after I-131 treatment, a significant increase of blood lymphocyte MN level was not observed. In addition, only the placebo group showed a significant, progressive increase in CFs activity. This peaked at the 14th day (p = 0.003 vs. baseline) and was still noted for the last plasma sample. The differences in the change in lymphocyte MN and CFs activity between the placebo and GBE-treated groups were significant (p < 0.01 and p < 0.05, respectively). Thyroid function tests, including serum thyroglobulin (Tg) and anti-Tg antibody levels, were never significantly different. Conclusions: GBE may protect from possible oxidative and genotoxic damage associated with I-131 treatment in patients requiring I-131 therapy for thyroid cancer, without affecting the clinical outcome. Further studies with larger cohorts of patients are needed to confirm this report and verify the beneficial effect of GBE in patients requiring I-131 therapy, particularly for those in whom repeated treatments and high activities of I-131 are required.