Contrary to popular belief, not only does taking the contraceptive pill not raise a woman’s chances of getting cancer, according to a new study her risk will probably go down. You can find this report in The British Medical Journal (BMJ). However, if a woman continues taking the contraceptive pill for over eight years her risk will then start to go up.

The contraceptive pill, or ‘The Pill’, was introduced in the 1960s. Since then over 300 million women are thought to have taken it. Even though it has been around for over 40 years, the writers explain that nobody has examined The Pill’s absolute risks and benefits.

Professor Philip Hannaford and team, from the University of Aberdeen, Scotland, looked at data which began in 1968 from the Royal College of General Practitioners (RCGP) Oral Contraception Study.

46,000 women were involved in the study, their average age being 29. About half of them had never taken oral contraceptives, while the other half had. Twice a year, each woman’s General Practitioner (GP) sent information to the study regarding the woman’s health. Plus, around three-quarters of the patients were identified at the National Health Service (NHS) central registries – information about their deaths or cancer were sent to the study, even if they had left the GP who recruited them.

The researchers explain that they used the data to work out the risks of developing any type of cancer and the main gynecological cancers combined. They also factored in such variables as smoking, social class and age.

As the study spanned nearly four decades, several GPs had not been able to provide updates throughout the whole period. The researchers calculated cancer risks using two sets of data. One set related to cancers while the women were still with the GP who recruited them – in this “GP observation dataset” the information was quite detailed. The other was from a database which received notification from the central NHS registries after women had left their recruiting GP.

After studying both data sets the team could not find any overall raised risk of cancer among women who had taken the pill. In fact, the GP observation dataset showed that women who had taken the pill had a 3% lower risk of developing any cancer. The other dataset showed a 12% lower risk of developing any type of cancer for women who had taken the pill.

A reduction of 12% means about one fewer case of cancer for every 2,200 women who have taken the contraceptive pill for one year. A reduction of 3% means one fewer case for every 10,000 women.

The scientists also found that women who had been taking the pill for more than eight years had a statistically significant increased risk of cancer. Just under a quarter of the women who took the pill did so for over eight years. These women had an especially higher risk of developing cervical cancer and cancer of the central nervous system. However, their risk of developing ovarian cancer was lower.

The authors say that according to the evidence they examined, the protective effect of taking the pill continues for about 15 years after stopping. They add that this study may be reassuring for the first generation of oral contraceptive takers.

The writers concluded “In this UK cohort oral contraception was not associated with an overall increased risk of any cancer; indeed it may even produce a net public health gain.”

“Cancer risk among users of oral contraceptives: cohort data from the Rotal College of General Practitioner’s oral contraception study.”
Philip C Hannaford, Sivasubramaniam Selvaraj, Alison M Elliott, Valerie Angus, Lisa Iversen, Amanda J Lee
BMJ, doi:10.1136/bmj.39289.649410.55 (published 11 September 2007)
Click here to view abstract online

Written by: Christian Nordqvist