Black cohosh and breast cancer: a systematic review.

2013-02-25
Integrative cancer therapies 13(1)
- Heidi Fritz
- Dugald Seely
- Jessie McGowan
- Becky Skidmore
- Rochelle Fernandes
- Deborah A Kennedy
- Kieran Cooley
- Raimond Wong
- Stephen Sagar
- Lynda G Balneaves
- Dean Fergusson

PubMed: 23439657
DOI: 10.1177/1534735413477191

Study Design

Type: Systematic Review
Population: women with or at risk of breast cancer
Methods: systematic review of MEDLINE, Embase, the Cochrane Library, and AMED from inception to July 2012 and October 2012 for human interventional or observational data

Background

Many women use black cohosh as a natural treatment for menopausal symptoms. However, controversy exists around safety in breast cancer, because of its purported estrogenic activity. We conducted a systematic review of black cohosh use in women with or at risk of breast cancer.

Methods

We searched MEDLINE, Embase, the Cochrane Library, and AMED from inception to July 2012 and October 2012 for human interventional or observational data pertaining to the safety and efficacy of black cohosh in patients with or at risk of breast cancer, including an assessment of the effect of black cohosh on estrogen responsive tissues.

Results

Of 450 records, we included 26 articles: 14 randomized controlled trials, 7 uncontrolled trials, and 5 observational studies.The evidence on efficacy for ho t flashes is divided, with some benefits seen when compared with baseline, but not when compared with placebo. Two observational studies found no association between black cohosh and risk of breast cancer, whereas 2 studies reported significant reductions in risk of primary breast cancer among postmenopausal women (adjusted odds ratio = 0.47, 95% confidence interval = 0.27-0.82), and risk of recurrence (adjusted hazard ratio = 0.75, 95% confidence interval = 0.63-0.89). Seventeen trials showed no significant impact on circulating hormone levels or proliferation in estrogen responsive tissues.

Conclusions

Current evidence does not support an association between black cohosh and increased risk of breast cancer. There is a lack of evidence supporting the efficacy of black cohosh for reduction of hot flashes in breast cancer patients. Given conflicting but promising results, and apparent safety, further research is warranted.

Research Insights

Black Cohosh→Reduced Breast Cancer Risk
Two observational studies found no association between black cohosh and risk of breast cancer
Effect
Neutral
Effect size
Small
Black Cohosh→Reduced Estrogen-responsive Tissue Proliferation
Seventeen trials showed no significant impact on ... proliferation in estrogen responsive tissues.
Effect
Neutral
Effect size
Small
Black Cohosh→Reduced Hormone Level
Seventeen trials showed no significant impact on circulating hormone levels
Effect
Neutral
Effect size
Small
Black Cohosh→Reduced Hot Flashes
evidence on efficacy for hot flashes is divided, with some benefits seen when compared with baseline, but not when compared with placebo.
Effect
Neutral
Effect size
Small
Black Cohosh→Reduced Recurrence
risk of recurrence (adjusted hazard ratio = 0.75, 95% confidence interval = 0.63-0.89)
Effect
Beneficial
Effect size
Moderate
Black Cohosh→Reduced Risk of Primary Breast Cancer
Two studies reported significant reductions in risk of primary breast cancer among postmenopausal women (adjusted odds ratio = 0.47, 95% confidence interval = 0.27-0.82)
Effect
Beneficial
Effect size
Large

Adverse Events Reported

Black Cohosh→circulating hormone levels or proliferation
Seventeen trials showed no significant impact on circulating hormone levels or proliferation in estrogen responsive tissues.
Finding
No significant difference
Significant
No
Black Cohosh→Overall tolerability
Given conflicting but promising results, and apparent safety, further research is warranted.
Finding
Reported