Background: Radioiodine (131I) therapy is performed in patients with differentiated thyroid cancer (DTC), either for thyroid remnant ablation or treating distant metastasis. Although 131I therapy is generally considered safe, a genotoxic damage has been demonstrated both in vivo and in vitro.
Aim: To evaluate the possible effect of Ginkgo biloba extract (EGb 761) supplementation on the time-course (up to 120 days) of clastogenic factors (CFs) and micronuclei (MN) appearance in lymphocytes from patients with DTC after thyroid remnant ablation, in a double-blind, placebo controlled study.
Methods: Nineteen patients with DTC (12 F, aged 3068 years; administered 131I activity: 2.965.50 GBq) were randomly assigned to EGb 761, 120 mg/day for 1 month (n=9, 6 F) or placebo (n=10, 6 F). Blood was taken at various intervals after 131I therapy (from 7 to 120 days), for the evaluation of the time-course of CFs and MN appearance in peripheral lymphocytes.
Results: In the placebo group, MN significantly increased after 131I therapy (P<0.001, ANOVA for repeated measures), peaking at 7th day (P<0.005) and slowly declining thereafter. Conversely, in EGb 761-treated patients, a slight not significant increase of MN without a peak was observed. Therefore, mean MN increment was significantly higher in placebo- than in EGb 761-treated patients (P<0.01). Moreover, an early (7th day, P<0.005) and sustained (P<0.01, ANOVA for repeated measures) MN increase induced by CFs was observed in the placebo group while, in EGb 761-treated patients it never reached the statistical significance. Again, mean MN increase induced by CFs was significantly higher in placebo- than in EGb 761-treated patients (P<0.05). Thyroid remnant resulted ablated in all the patients.
Conclusions: Although 131I therapy is essentially safe, our data encourage for the use of Ginkgo biloba extract to prevent possible harmful genetic effects, particularly in patients with metastasis who require repeated radioiodine treatments.