Record ID: MS-N090
Family: Botanicals and nutraceuticals
Clinical question: Does a standardized green-tea catechin extract prevent prostate cancer in men with HGPIN or ASAP?
Evidence label: Randomized trial; negative primary endpoint
Evidence at a glance
Benefit: No statistically significant reduction in prostate-cancer diagnoses at one year.
Certainty: Low. One small prevention trial, limited follow-up and secondary signals that do not rescue the primary result.
Risk: Concentrated extracts can cause gastrointestinal effects, raise liver enzymes and rarely cause clinically important liver injury; interactions are possible.
Cancer control: This was prevention research in high-risk biopsy findings, not treatment of established cancer.
What was studied
A 2015 placebo-controlled phase II trial enrolled 97 men with high-grade prostatic intraepithelial neoplasia (HGPIN) or atypical small acinar proliferation (ASAP). Participants received a standardized decaffeinated catechin mixture supplying 400 mg/day of EGCG or placebo for 12 months.
The clinical endpoint was a prostate-cancer diagnosis on follow-up biopsy. Brewed tea, other extracts and products labeled only by total “green tea” weight are not equivalent to the studied formulation.
What the results mean
Cancer was diagnosed in 5 of 49 men assigned extract and 9 of 48 assigned placebo (about 10% versus 19%; P=.25). The primary endpoint was not met.
A favorable secondary composite included another biopsy abnormality and was driven by fewer diagnoses of that abnormality. PSA and biomarker changes cannot establish fewer metastases or longer survival.
Limits and uncertainty
The study was underpowered for a modest prevention effect and followed participants for only one year. Multiple reports of the same trial are not independent trials.
A broad Cochrane review found inconsistent results across study designs and cancer sites; observational tea-drinking studies cannot validate a capsule regimen.
Safety and practical context
NCCIH distinguishes ordinary brewed tea from concentrated tablets and capsules. Liver injury is uncommon but has been reported primarily with extracts. Medication interactions include reduced exposure to nadolol and atorvastatin.
Stop and seek advice for dark urine, jaundice or persistent abdominal pain. A “below 800 mg EGCG” label is not a proven safe threshold for every person.
Questions for the care team
- Is this a beverage or a concentrated extract, and how much EGCG does it contain?
- Do liver disease or my medicines increase risk?
- Was the claim based on the negative primary endpoint or a secondary biomarker?
- What surveillance remains necessary regardless of supplement use?
Sources
- Randomized prevention trial (PMID 25873370)
- Cochrane review of green tea and cancer prevention
- NCCIH green tea safety guidance
- Connected Missing Script review
Funding and conflicts
The trial report should be consulted for complete sponsor and conflict details. This record does not treat an extract manufacturer’s standardization claim as independent evidence.
Last literature search: October 21, 2026
Record appraised: October 21, 2026
This educational record is not individualized medical advice. Research doses and schedules are not personal prescriptions; do not delay or replace evidence-based cancer care.
