Breast Cancer

EGCG is the main anticancer catechin in green tea, and breast cancer is one of the most studied cancer types in the EGCG literature.

Related treatment context

If the practical question is ER-positive, HER2-negative disease on abemaciclib or ribociclib, also see CDK4/6 Options and Supplement Considerations.

That page covers the CDK4/6-specific supplement question, including liver, platelet, and monitoring overlap.

Overview

The evidence spans epidemiology, biomarker studies, subtype-specific laboratory work, and combination research with endocrine and HER2-focused therapy.

Key human data

Two Japanese studies found that women who reported drinking more green tea before their breast cancer diagnosis had fewer subsequent recurrences, particularly in early-stage disease. These studies show a possible link—not proof that green tea prevents recurrence. They also do not establish that starting green tea or EGCG supplements after diagnosis provides the same benefit.

Key preclinical data

• EGCG inhibits HER2 phosphorylation and downstream signalling in HER2-overexpressing models

• In triple-negative breast cancer, EGCG suppresses PI3K/Akt/mTOR and invasion-related signalling

• Synergy with tamoxifen has been shown in ER-positive models

• Lipid nanoparticle EGCG has shown selective cytotoxicity in breast cancer models, including tamoxifen-resistant cells

Clinical positioning

Best viewed as adjunctive and preventive rather than curative. The most credible practical roles are long-term support, recurrence-focused strategies, and combination discussion in hormone-sensitive or pathway-driven disease.

References

The roles of epigallocatechin gallate in the tumour microenvironment, metabolic reprogramming, and anti-cancer therapy
https://www.frontiersin.org/articles/10.3389/fimmu.2024.1331641/full

Epigallocatechin-3-Gallate Therapeutic Potential in Cancer: Mechanism of Action and Clinical Implications
https://pmc.ncbi.nlm.nih.gov/articles/PMC10343677/