London - Almost half of women with breast cancer could have their treatment transformed by a readily available hormone found in the Pill.
In a landmark study, Cambridge University researchers have shown that progesterone - an inexpensive drug used in contraceptives - slows the growth of tumours.
In lab tests, it made tamoxifen, the gold standard breast cancer medicine, work twice as well as usual. As a result, experts believe it could be a life-saver.
Despite advances in medicine and improvements in survival, breast cancer still claims the lives of almost 1 000 women a month.
It is thought progesterone may work in nearly half of the 55 000 cases diagnosed each year, meaning tens of thousands of women and their loved ones could benefit from the breakthrough.
With tests on women being planned and progesterone both cheap and safe, experts said the “exciting” research was “a big step forward’”
The journal Nature said it was “time to rethink breast cancer”.
Researcher Jason Carroll said: “The results are pretty clear and potentially have direct benefits for many women with breast cancer.’”
Dr Carroll’s research centres on tumours that are fuelled by the hormone oestrogen.
Some of these are also sensitive to progesterone, a hormone used in contraception.
Dr Carroll, who is funded by Cancer Research UK, showed that in this type of tumour, progesterone “talks” to the oestrogen that is trying to feed the tumour. This stops the cancer from growing as quickly.
In tests on mice with tumours, giving progesterone at the same time as tamoxifen, a drug widely used to stop breast cancer coming back after surgery, had a dramatic effect.
Cancers treated with the progesterone-tamoxifen combination grew half as quickly as those given tamixofen alone, the journal Nature reports.
The researchers cautioned that much more work is needed to prove that the progesterone-tamoxifen combination has the same effect in women. It also too early to say whether the hormone would be given as a pill or a jab or how often it would need to be taken.
However, if progesterone does fulfil its promise, it could help almost half of women with breast cancer - more than 20 000 women a year. Dr Emma Smith of Cancer Research UK said it could be a life-saver. She said: “This exciting study in cells shows how a cheap, safe and widely-available drug could potentially improve treatment for around half of all breast cancer patients.
“Thanks to research, almost 70 percent of women now survive breast cancer beyond 20 years - but so much more could be done.”
Dr Richard Berks, of charity Breast Cancer Now, said: “This is a fascinating finding.
“Further research is now needed to help understand whether progesterone could benefit patients; if successful, this could be a cheap and effective treatment that benefits tens of thousands of women with breast cancer.
“This is a prime example of how research is critical in helping not just to develop new treatments but also to improve the treatments we already have, which will be essential if we are to stop women dying from breast cancer.
“We very much look forward to the results of future work in this particular area.” Samia al Qadhi, chief executive of charity Breast Cancer Care, said: “These findings are an exciting development in our understanding of how hormones may make certain breast cancers grow.
“There are 55 000 women every year in the UK dealing with the overwhelming news they have breast cancer, so any research to help improve treatments can only be welcomed.”
Daily Mail