Evaluation of oxidative stress and antioxidative action of green tea catechins in patients treated with tamoxifen: a randomized open-label,crossover study

Abstract

The relation between oxidative stress and tamoxifen is not completely clear, since some studies attribute a possible antioxidant action, while others describe several pro-oxidative effects. The aim of this study was to evaluate oxidative stress in patients treated with tamoxifen and the effect of administration of green tea catechins on this parameter. Tests aimed at evaluating the derivatives of reactive oxygen metabolites (d-Roms test) and the antioxidant reserve (BAP test) were adopted to estimate oxidative stress. Subjects treated with tamoxifen received Categ [Sofar] (green tea extract with 200 mg of catechins, 2 tablets twice a day for 3 weeks), according to a crossover design. High or very high antioxidant stress levels were found in all the 46 patients treated with tamoxifen, while in a control group of 18 patients treated with aromatase inhibitors or who had no longer been treated with tamoxifen for 1 year or more, high or very high oxidative stress levels were found in 66.7% of cases (p < 0.0001). The antioxidant reserve was low in 52% of patients treated with tamoxifen versus 40% of the patients in the control group, but the difference was not statistically significant (p = n.s.). The levels of oxidative stress and antioxidant reserve did not change significantly in a subgroup where the patients took Categ for 3 weeks followed by 3 weeks washout (group A), while there was a statistical significant reduction in the levels of oxidative stress (p < 0.05) and an increase in the antioxidant reserve (p < 0.01) in the subgroup where 3 weeks of no treatment were followed by 3 weeks of treatment with Categ (group B). In conclusion, our study confirms a pro-oxidant effect of tamoxifen. The supplementation with green tea catechins gave discordant results. A high number of variables might intervene in the delicate oxidative–reductive equilibrium of human beings and, despite progress achieved in the last few years, there are several aspects concerning the oxidative–reductive equilibrium that still have to be explained.