The Pharmaceutical Journal
Vol 279 No 7469 p281
15 September 2007

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Contraceptives do not raise overall cancer risk

Taking the oral contraceptive pill is not associated with an overall increased risk of cancer and may even produce a net public health gain, according to a study published on BMJ Online First this week (12 September 2007).

However, the researchers identified an increased risk for women who took oral contraceptives for more than eight years.

Researchers analysed data spanning 36 years from the Royal College of General Practitioners oral contraception study, which recruited 46,000 women, half of whom were using oral contraceptives; the other half had never taken them.

They calculated the cancer risks using two sets of data — one that related to cancers reported while the women remained registered with their recruiting GP (GP observation dataset) and another that included cancers notified by the central NHS registries after women had left their recruiting GP (main dataset).

In the main dataset, the researchers found that women who had used oral contraceptives had a 12 per cent reduction in risk of any cancer (relative risk 0.88, 95 per cent confidence interval 0.83–0.94). Significant reductions were found in rates of cancer of the large bowel or rectum, uterine body and ovaries and other sites.

Conversely, non-significant increases were found in the risk of cancers of the lung, cervix, central nervous system and pituitary. No difference was found for the risk of breast cancer.

When the GP observation dataset was used the reduced risk of developing any cancer was not significant (0.97, 0.88–1.06).

The researchers also observed that women who used oral contraceptives for more than eight years had a 22 per cent increased risk of any cancer (1.22, 1.07–1.39). However prolonged use was also associated with a 62 per cent reduced risk of ovarian cancer (0.38, 0.16–0.88).

Most of the pills used were combined oral contraceptives containing oestrogen 50µg.

“Many women, especially those who used the first generation of oral contraceptives many years ago, are likely to be reassured by our results,” say the researchers. However they add that their findings might not reflect the experience of women using oral contraceptives today.