Black Cohosh and treatment of menopausal flushing in Breast cancer patients
By Dr V Masharani
A query from one of the local pharmacists [ thanks Dee!]
made me look in to the issue of the use of Black Cohosh in the treatment of the
quite debilitating menopausal flushing patients with breast cancer can get,
especially those on Tamoxifen.
Recent studies have highlighted the increased risks of
getting breast cancer from taking hormone replacement therapy (HRT).
Subsequently the two trials looking at the use of HRT in symptomatic breast
cancer patients have been suspended. So what are the other choices?
Of the herbs, Black Cohosh is the most popular. Like many
herbal preparations there are few clinical studies that give us all the answers
about its effectiveness or safety.
It is thought to work by acting as a mild oestrogen – the
hormone missing when you hit the menopause. The problem is that some breast
cancers are oestrogen sensitive so would grow quicker under the influence of oestrogens.
Tamoxifen is a drug commonly given to breast cancer patients to block the
oestrogen action in the body so it is not surprising that those patients suffer
more from menopausal flushing.
A good summary of the pharmacology of Black Cohosh was published
in the American Family Physician in July 2003 (ref 1) and I have summarised
below what I found when I carried out a literature search on this topic.
8 studies involving about 2000 patients showed a benefit
equivalent to oestrogen. There were, however, serious flaws in the design of
these trials so it is difficult to know for sure that the results are accurate.
Other studies did not show a benefit (ref 2). The studies all involved very
small numbers of people. The American College of Obstetricians and
Gynecologists looked at the reseach evidence in 2001 and produced a consensus
statement stating that Black Cohosh my be helpful in the short term (6 months
or less) (ref 3).
There are several reports that taking Black Cohosh decreases
the effectiveness of Tamoxifen. So discussing the use of this herb with the
oncology doctor is essential.
“Black Cohosh may increase breast cancer spread” was
reported in several American journals last year (ref 4) but this report is about
mice studies that show that although there were no more cancers in mice given
the herb, the ones that did seem to have a more aggressive form of the disease.
A previous study (ref 5) looked at the growth of breast cancer tumours in rats
showed that those given Black Cohosh did not develop bigger cancers than those
not given it. I could not find any trials on humans.
Several concerns have been expressed about the use of Black
Cohosh in breast cancer patients. There is very little good evidence either way
in terms of safety or risk or effectiveness.
A good article (ref 6) summarises the management of hot
flushes in breast cancer patients. Personally I am favouring the use of some of
the newer antidepressants for this condition as they seem moderately effective
and are no serious safety concerns about them.
Ref1. Black Cohosh. Kligler American Family
Physician. 68:1: July 1 2003. 114-116
Ref3Questions
and Answers About Black Cohosh and the Symptoms of Menopause.pdf
Ref4Black
Cohosh May Increase Breast Cancer Spread.pdf
Clin J
Oncol Nurs 2003 Nov-Dec; 7(6): 637-40.