The effect of Ginkgo biloba extract on genotoxic damage in patients with differentiated thyroid carcinoma receiving thyroid remnant ablation with iodine-131.

BACKGROUND: Radioiodine ((131)I) therapy is usually performed in patients with differentiated thyroid cancer (DTC). Although (131)I 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 (131)I 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 (131)I 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 (131)I 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 (131)I 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 (131)I 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 (131)I treatment in patients requiring (131)I 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 (131)I therapy, particularly for those in whom repeated treatments and high activities of (131)I are required.

Recombinant human thyroid-stimulating hormone is effective for radioiodine ablation of post-surgical thyroid remnants.

OBJECTIVE: To investigate whether recombinant human thyroid-stimulating factor (rhTSH) is effective for the radiometabolic ablation of post-surgery thyroid remnants, using low doses of (131)I. PATIENTS AND METHODS: The study included two groups of patients enrolled consecutively: group 1 consisted of 52 patients with papillary cancer or minimally invasive follicular cancer (stage I and II), and group 2 consisted of 41 patients with the same stage of disease. All patients underwent a total thyroidectomy. Group 1 received 1.11 GBq (30 mCi) (131)I for post-surgical remnants ablation with the aid of rhTSH, while group 2, in the hypothyroid state, received the same amount of radioiodine. To minimize iodine interference, all patients remained on a low iodine diet for 2 weeks and L-thyroxine (L-T4) was stopped for 4 days in the group of patients treated with the aid of rhTSH. To investigate (131)I uptake in this group, a tracer dose was administered 3 h after the second injection of rhTSH and the uptake was evaluated at 24 h just before administration of the therapeutic dose. I was also measured in the patients treated in the hypothyroid state just before the therapeutic dose was given. RESULTS: After 1 year both groups were studied by using whole-body scintigraphy (WBS) and measuring thyroglobulin after rhTSH. In group 1, WBS was negative in 76.9% (40 patients), while thyroglobulin-stimulated levels were <1.0 ng . ml(-1) in 86.5% (45 patients). In Group 2, WBS was negative in 75.6% (31 patients), while thyroglobulin-stimulated levels were <1 ng . ml(-1) in 78.0% (32 patients). (131)I uptake was 2.29+/-0.45 in the group treated with the aid of rhTSH, and 3.30+/-0.7 in the group treated in the hypothyroid state (P=0.2). No patients treated with the aid of rhTSH and with the short stoppage of L-T4 experienced symptoms of hypothyroidism, and free thyroxine (FT4) and thyroid-stimulating hormone levels remained normal. CONCLUSIONS: Our data confirm that, when the interference of iodine is minimized, rhTSH is highly effective for the treatment of post-surgical thyroid remnants using a low dose of (131)I.