Green tea extract/catechin supplementation for secondary prevention of metachronous colorectal adenomas after polypectomy.

Abstract

e15670 Background: Green tea extracts (GTE) have proposed protective effects in colorectal neoplasia, but randomized evidence remains inconsistent. We performed a meta-analysis of randomized controlled trials (RCTs) evaluating oral GTE supplementation following colorectal adenoma resection. Methods: We systematically reviewed RCTs enrolling adults after complete adenoma removal and a surveillance colonoscopy confirming no residual adenomas. Interventions were oral GTE initiated post-polypectomy versus standard surveillance. The primary endpoint was colorectal adenomas (≥1) at surveillance colonoscopy; secondary endpoint was advanced adenomas. Risk ratios (RR) were pooled using random-effects models; heterogeneity was assessed with I². Risk of bias was evaluated using Cochrane RoB2. Absolute risk reduction (ARR) and number needed to treat (NNT) were calculated at specified surveillance intervals. Results: Three RCTs were included (n = 900; 441 GTE vs 459 control); 900 randomized participants completed surveillance colonoscopy and contributed to primary analysis. Overall, GTE was not associated with statistically significant reduction in adenomas (pooled RR 0.69, 95% CI 0.44–1.07; p = 0.10), with substantial heterogeneity (I² = 69%). Differences in follow-up duration and exposure likely contributed, including short-term supplementation (0.9–1.5g/day) versus prolonged standardized decaffeinated extract (300mg day) with endpoint colonoscopy at 26–44 months. In sensitivity analysis restricted to the two 12-month trials, GTE significantly reduced adenomas (RR 0.53, 95% CI 0.36–0.80; p = 0.002; I² = 0%), corresponding to recurrence rates of 19.7% (26/132) vs 36.8% (50/136) (ARR 17.1%; NNT≈6). In contrast, the 3-year MIRACLE trial showed attenuated benefit (51.1% vs 55.7%; RR 0.92; ARR 4.6%; NNT≈22), with no reduction in advanced adenomas (RR 0.97) [Table 1]. Conclusions: GTE supplementation did not significantly reduce colorectal adenomas overall, with substantial heterogeneity. Apparent benefits in short-term trials were not sustained with longer follow-up, and advanced adenoma rates were unchanged. Future trials with harmonized dosing, formulation, and surveillance intervals are needed to clarify clinical relevance. Study Experimental Events/Total Control Events/Total Weight (%) Risk Ratio 95% CI Seufferlein 2022 158/309 180/323 47.2 0.92 0.79–1.06 Shimizu 2008 9/60 20/65 22.1 0.49 0.24–0.99 Shin 2018 17/72 30/71 30.7 0.56 0.34–0.92 Total (Random Effects) 184/441 230/459 100.0 0.69 0.44–1.07 Heterogeneity — — — Tau² = 0.10; χ² = 6.39 (df = 2) P = 0.04; I² = 69% Test for overall effect — — — Z = 1.67 P = 0.10 Total (Random Effects) (excluding Seufferlein 2022) 26/132 50/136 100.0 0.53 0.36-0.80 Heterogeneity (excluding Seufferlein 2022) — — — Tau² = 0.00; χ² = 0.10 (df = 1) P = 0.76; I² = 0% Test for overall effect (excluding Seufferlein 2022) — — — Z = 3.03 P = 0.002