Women taking contemporary high-oestrogen birth control pills, and a few other formulations, are at an increased risk of breast cancer, suggests new research. The study also found that oral contraceptives with low doses of oestrogen did not increase users’ risk of developing breast cancer.
While previous studies have already found a link between birth control pills and breast cancer risk, this research, published in Cancer Research, is the first of its kind to look at the risks for specific hormone combinations in oral contraceptives. You can read more in the American Association for Cancer Research’s press release.
This study, unlike earlier research, used electronic pharmacy records to get specific information about the types of oral contraceptives being taken, rather than relying on self-reported accounts from individuals.
According to the Ministry of Health, breast cancer is New Zealand’s third most common cancer and accounts for more than 600 deaths every year.
Our colleagues at the UK SMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).
Prof Monserrat Garcia-Closas, Professor of Epidemiology at The Institute of Cancer Research, comments:
“We have known for a long time that recent use of oral contraceptives can result in small increases in breast cancer risk, based on results from multiple studies. But this study has current relevance because most previous studies are based on earlier types of contraceptive, and there has been debate on whether current formulations are still related to risk.
“This paper suggests that some, but not all, newer formulations of oral contraceptive are related to increased risk of breast cancer. If confirmed in further studies, it might help lead to the recommendation of specific formulations that are effective contraceptives but do not increase breast cancer risk – for instance, low dose oestrogen contraceptives.
“But this, or previous data does not lead to the conclusion that women who are currently taking the pill should stop. There is a balance between its desirable effects – including a reduced risk of ovarian cancer and benign breast conditions, as well as preventing pregnancy – and undesirable effects such as a small increased breast cancer risk.
“Another consideration is that the risk of breast cancer for most women using oral contraceptives in their 20s and 30s in absolute terms is quite low, and the effect of the pill on breast cancer risk seems to be short-lived. In contrast, the protective effects against ovarian cancer seem to be long lasting.”
Sarah Williams, Senior Health Information Officer at Cancer Research UK, comments:
“Women shouldn’t stop taking the Pill on the basis of this study. It can’t tell us whether newer versions of the Pill affect the risk of breast cancer in a different way from older versions. Not only could many of the findings about different types of Pill be down to chance, the study also failed to fully account for things like age, family history of breast cancer, or whether a woman had recently been for breast screening. And the research doesn’t consider whether or for how long women had used the Pill previously.
“The Pill is already known to have effects on several different cancers: breast and cervical cancer risk is raised while a woman is taking it, but goes back down again within 10 years of stopping. But the Pill also offers lasting protection against ovarian and womb cancers for decades after women stop using it. On balance the Pill prevents more cases of cancer than it causes.
“The primary reason for taking the pill is contraception. If women are worried about the Pill’s side-effects they should discuss options with a GP or family planning service to help decide what’s right for each individual.”
Prof Dame Valerie Beral, Director of the Cancer Epidemiology Unit at the University of Oxford, comments:
“It has been known for about 20 years that recent users of the pill have a transient, and small, increase in breast cancer risk. This conclusion was based on a meta-analysis of over 50 studies, including individual information on pill use in some 50,000 women with breast cancer. The authors of this new Cancer Research publication contributed to the meta-analysis.
“There is little new in the Cancer Research publication. Furthermore, it is just one of over 50 studies that have investigated the association between use of the pill and breast cancer risk, and findings from a single study should not be considered in isolation.”