Is there any evidence to support use of green tea capsule/tablet supplements or extracts for reduction in breast cancer recurrence rates?

Is there any evidence to support use of green tea capsule or tablet supplement or extracts for reduction in breast cancer recurrence rates?

Comment by InpharmD Researcher

The majority of data exploring the impact of green tea on breast cancer is limited to its consumption as a drink and literature specific to green tea supplements given in capsule/tablet form is lacking. One randomized trial utilized green tea extract, administered as four daily decaffeinated capsules, to assess potential chemoprotective effects via mammographic density after 12 months, finding no significant effects. Thus, no conclusive evidence could be identified to support the use of green tea supplements to reduce recurrence of breast cancer.

Background

Green tea has attracted significant research interest over the past few decades for its potential health benefits, particularly its anti-cancer properties. A 2014 review article discusses various epidemiological studies that examine the relationship between green tea consumption and breast cancer prevention. Initial findings from a 1997 study indicated that increased green tea intake may reduce breast cancer risk, especially among women consuming over ten cups daily. Subsequent meta-analyses have also explored this association. A 2010 meta-analysis assessed two studies on breast cancer recurrence and seven on breast cancer incidence and suggested that heavy green tea drinkers (>3 cups daily) had a non-significant 27% reduction in recurrence rate and a statistically significant 19% reduction in breast cancer incidence. However, cohort studies did not demonstrate a significant association with breast cancer incidence. Additional evidence suggests that green tea may have enhanced protective effects against breast cancer when consumed in combination with other dietary components, such as soy and mushrooms. A study of Asian-American women found that green tea consumption was linked to a lower breast cancer risk among those with low soy intake, while no such association was seen in those with high soy intake. Another study suggested that higher mushroom consumption correlated with reduced breast cancer risk in Chinese women, and combining mushrooms and green tea further lowered this risk. The authors note that these findings suggest that combining green tea with other beneficial dietary components may enhance its protective effects against breast cancer. Overall, the authors emphasize that the epidemiological evidence assessing the relationship between green tea consumption and breast cancer prevention remains inconclusive, and while there is some evidence suggesting that high green tea intake may reduce the risk of breast cancer recurrence and incidence, further research is needed to clarify these associations. Of note, the use of capsule and tablet green tea supplement formulations specifically to reduce the recurrence of breast cancer is not addressed within the review. [1], [2]

While more tangentially related meta-analyses have been published, much of the data exploring the use of green tea and potential effect on breast cancer again focuses on its consumption as a tea as opposed to administration via capsule- or tablet-based supplements. These recent systematic reviews and meta-analyses have pooled data to investigate possible benefits for individuals who regularly drink green team, with a 2024 meta-analysis suggesting a 44% reduced risk of recurrence of stage 1 and II breast cancer with prediagnostic green tea (hazard ratio 0.56, 95% confidence interval [CI] 0.38 to 0.83). Both studies were relatively dated, and both were designed as hospital-based prospective cohort studies conducted in Japan. A previous 2018 systematic review and meta-analysis included 13 observational studies, finding a potential protective effect of green tea consumption on risk of breast cancer, particularly for recurrence of breast cancer, as indicated by an inverse statistically significant relationship between green tea and breast cancer, with an odds ratio of 0.85 (95% CI 0.80 to 0.92; p= 0.000). Quantity of green tea consumed within individual studies generally ranged from 3 to 8 cups/day. [3], [4]

Literature Review

A search of the published medical literature revealed 2 studies investigating the researchable question:

Is there any evidence to support use of green tea capsule or tablet supplement or extracts for reduction in breast cancer recurrence rates?

Level of evidence

X - No data Read more→

Please see Tables 1-2 for your response.

A Randomized Controlled Trial of Green Tea Extract Supplementation and Mammographic Density in Postmenopausal Women at Increased Risk of Breast Cancer
Design	Randomized, double-blind, placebo-controlled phase II clinical trial N= 1,075
Objective	To evaluate the effects of daily consumption of green tea extract (GTE) containing 800 mg EGCG for 12 months on changes in mammographic density (MD) measures in healthy postmenopausal women at high risk of breast cancer due to dense breast tissue
Study Groups	GTE (n= 538) Placebo (n= 537)
Inclusion Criteria	Healthy postmenopausal women aged 50 to 70 years old with "heterogeneously dense" or "extremely dense" breast tissues (>50% fibroglandular tissue)
Exclusion Criteria	Current smokers, drinking more than one cup of green tea or 7 alcoholic drinks per week, Body mass index (BMI) >40.0 or <18.5, compromised liver function, history of breast cancer or any other cancer in the past 5 years, current or prior users of certain medications, significant weight change in the last year, or planning to participate in any weight loss or gain program during the trial
Methods	Participants consumed daily 4 decaffeinated GTE capsules containing 1,315 mg total catechins, including 843 mg EGCG for 12 months. MD was assessed using the Madena method in digital mammograms at baseline and month 12. Compliance was confirmed by pill count, pill diary, and urinary catechin concentrations.
Duration	12 months
Outcome Measures	Primary: Percent Mammographic Density (PMD), Absolute Mammographic Density (MD) Secondary: Volumetric-based MD (FGV%) in a subset of participants
Baseline Characteristics		GTE (n= 462)	Placebo (n= 470)
	Age, years	60.0 ± 4.9	59.6 ± 5.0
	BMI kg/m²	25.1 ± 3.7	25.1 ± 3.7
	Non-Hispanic White	97.9%	96.6%
	Parity Parous Nulliparous	76.4% 23.4%	75.7% 23.2%
	Never Smokers	68.2%	68.1%
	Family history of breast cancer (first-degree relative)	25.8%	24.0%
Results		GTE (n= 462)	Placebo (n= 470)
	Change in PMD, %	-0.58*	-0.64*
	Change in Absolute MD, %	1.06	1.70
	*p= 0.97 GTE supplementation for 12 months did not significantly change percent MD (PMD) or absolute MD in all women. In younger women (50–55 years), GTE supplementation significantly reduced PMD by 4.40% as compared with the placebo with a 1.02% PMD increase from pre- to postintervention (p= 0.05), but had no effect in older women (p_interaction= 0.07). GTE supplementation did not induce MD change in other subgroups of women stratified by catechol-O-methyltransferase genotype or level of body mass index.
Adverse Events	The study intervention was well tolerated, and the total frequencies of reported adverse events were similar between the two groups.
Study Author Conclusions	One-year supplementation with a high dose of EGCG did not have a significant effect on MD measures in all women, but reduced PMD in younger women (50-55 years), suggesting an age-dependent effect similar to those of tamoxifen. Further investigation of the potential chemopreventive effect of green tea intake on breast cancer risk in younger women is warranted.
Critique	Despite the high compliance and use of a highly reproducible method for MD assessment, this study is limited by lack of data on past green tea consumption, difficulty in recruiting participants with high activity COMT genotype, and potential bias due to the gap between mammograms and baseline clinic visits.

References:

Samavat H, Ursin G, Emory TH, et al. A Randomized Controlled Trial of Green Tea Extract Supplementation and Mammographic Density in Postmenopausal Women at Increased Risk of Breast Cancer. Cancer Prev Res (Phila). 2017;10(12):710-718. doi:10.1158/1940-6207.CAPR-17-0187

The Minnesota Green Tea Trial (MGTT), a randomized controlled trial of the efficacy of green tea extract on biomarkers of breast cancer risk: Study rationale, design, methods, and participant characteristics
Design	Randomized, double-blind, placebo-controlled trial N= 1,075
Objective	To determine the effects of 12-month daily green tea catechin supplementation (green tea extract [GTE]) on biomarkers of breast cancer risk in postmenopausal women
Study Groups	GTE (n= 538) Placebo (n= 537)
Inclusion Criteria	Aged 50-70 years old, generally healthy postmenopausal women, heterogeneously (51-75% glandular) or extremely (<75% glandular) dense breasts
Exclusion Criteria	Regular green tea intake; hepatitis B or C viral infection; elevated liver enzymes >1.5 times upper limit of normal; current or prior use of hormone therapy, including systemic postmenopausal hormone therapy, chemopreventive agents or aromatase inhibitors; previous diagnosis of breast cancer, proliferative breast disease, or ovarian cancer; history of any other malignancy in previous 5 years; presence of breast implants; currently taking methotrexate or etanercept; body mass index (BMI) <18.5 or >40 kg/m²; ongoing enrollment in a weight loss or weight gain program; weight change >10 lbs in previous year; alcohol intake >7 drinks per week; current smoker
Methods	Patients were randomized to receive two GTE capsules or two placebo capsules twice daily for 12 months. Participants were further stratified by catechol-O-methyltransferase (COMT) genotype (high activity or law activity). The GTE supplement contained 1,315 ± 115 mg catechins containing 843 ± 44 mg epigallocatechin gallate (EGCG; equivalent to 10 grams of dry tea leaves or five 8-ounce cups of brewed green tea). Placebo capsules were identical in appearance and contained maltodextrin (50%), cellulose (49.5%), and magnesium stearate (0.5%). Blood and urine were collected throughout the trial for biomarker and compliance evaluation.
Duration	Recruitment: August 2009 to April 2013 Intervention: 12 months
Outcome Measures	Compliance, urinary levels of epigallocatechin (EGC) and epicatechin (EC), dropout rates
Baseline Characteristics		GTE (n= 538)	Placebo (n= 537)
	Age, years	59.9 ± 5	59.6 ± 5.1
	Female	100%	100%
	White	95.7%	94%
	COMT genotype High Intermediate Low	26.8% 40.2% 33.1%	26.3% 43.4% 30.3%
	Family history of breast cancer	24.2%	22.9%
	Age at menopause, years	49 ± 5.8	49.2 ± 5.3
	Years since menopause	10.9 ± 7.8	10.3 ± 7.2
	Past use of oral contraceptives	84.6%	82.7%
	Past use of hormone therapy	40.2%	40.2%
	BMI, kg/m²	25.2 ± 3.7	25 ± 3.9
	Use of vitamin supplements	88.7%	83.2%
	Smoking status Never Former Unknown	66.4% 31% 2.6%	66.3% 30.9% 2.8%
Results	Participants in both groups took an average of 96.5% of prescribed capsules. Urinary levels of catechins including EGC and EC were similar between groups at baseline but were significantly higher in the GTE participants all time points thereafter. Participants in the GTE group experienced an average 10.6-fold and 16.5-fold increase in urinary levels of EGC and EC compared to placebo, respectively. Significant positive correlations were identified between the pill counts and urinary levels of EGC and EC among participants in the GTE group during the first 3 months of intervention (p= 0.03 for EGC; p= 0.02 for EC). Overall dropout rate was 12.8% (13.9% for GTE and 11.7% for placebo). Characteristics did not differ between GTE and placebo dropouts except for higher weight in placebo-dropouts than GTE-dropouts.
Adverse Events	Not disclosed
Study Author Conclusions	In summary, the MGTT enrolled 1,075 participants and completed the trial for 937 women during 2009–2014. The MGTT is the largest long-term study investigating the effects of green tea catechins on well-known biomarkers of breast cancer among postmenopausal women at high risk of breast cancer. This study aims to elucidate the mechanisms by which green tea may reduce breast cancer risk, potentially identifying subgroups of women who may benefit from green tea intake, and lead to improved dietary recommendations for breast cancer prevention.
InpharmD Researcher Critique	This study lacks any evaluation of clinical outcomes. The results of this analysis are largely theoretical.

References:

Samavat H, Dostal AM, Wang R, et al. The Minnesota Green Tea Trial (MGTT), a randomized controlled trial of the efficacy of green tea extract on biomarkers of breast cancer risk: study rationale, design, methods, and participant characteristics. Cancer Causes Control. 2015;26(10):1405-1419. doi:10.1007/s10552-015-0632-2