Green tea and green tea extract in oncological treatment: A systematic review

Purpose: Teas are an essential part of traditional phytotherapy. The aim of this systematic review is to assess the clinical evidence using green tea catechins in cancer care. Methods: A systematic search was conducted searching five electronic databases concerning the effectiveness and risks of epigallocatechin gallate (EGCG) on cancer patients. Results: Seven studies with 371 patients were included. Patients were mainly suffering from breast and prostate cancer. Dosing ranged from 28 mg to 1600 mg EGCG, intervention time from 7 days to 6 months with different applications (topical 2 studies; oral 5 studies). The studies showed heterogeneous methodological quality and results leading not to conduct a meta-analysis. There was a small decrease in prostate-specific-antigen levels in one study (N=60; T0:(mean±SD) 9.6±5.2 ng/ml, T1: 8.4±4.3 ng/ml vs. T0: 9.9±8.5 ng/ml, T1: 10.0±9.0 ng/ml; p=0.04), whereas in a second study only a trend was seen. Topical green tea was as effective as metronidazole powder in reducing the odor of fungating malignant wounds (1 study; N=30) with a consequent increase in quality of life (QoL) (p<0.001), improvement of appetite (p<0.001), malodorous control (p<0.001), social activities (p<0.001). Radiotherapy-induced diarrhea was lower in the green tea intervention group compared to placebo (1 study; N=42; week 4+5: without diarrhea p=0.002). Conclusions: The studies suggest that EGCG is as effective as a local antibiotic in malodorous control and improvement of QoL of fungating malignant wounds. Green tea could be a possible complementary method for treating acute radiation-induced diarrhea. Due to limitations, further studies with higher methodological quality and larger sample sizes are needed.