London: New types of combined oral contraceptives — containing both oestrogens and progestogens — may reduce the risk of ovarian cancer in young women, a study has found.
The study, published by The BMJ, showed that this positive effect strengthened with longer periods of use and persisted for several years after stopping, providing important reassurance for women. At least 100 million women worldwide are using hormonal contraception every day.
Previous research has shown a reduced risk of ovarian cancer in women who take combined oral contraceptives, but most of the evidence relates to the use of older products, containing higher levels of oestrogen and older progestogens. Women who use newer oral contraceptives and other hormonal contraceptive methods also want to know whether they are likely to experience the same benefit.
Researchers at the University of Aberdeen in Scotland and the University of Copenhagen in Denmark investigated the influence of newer hormonal contraceptives (combined and progestogen-only products) on overall and specific types of ovarian cancer in women of reproductive age. They analysed data for nearly 1.9 million Danish women aged 15-49 years between 1995 and 2014.
Women were categorised as never users, current or recent users (up to one year after stopping use), or former users (more than one year after stopping use) of different hormonal contraceptives. Most (86 per cent) of the hormonal contraceptive use related to combined oral products, researchers said.
After taking account of several factors, including age and parity, the researchers found that the number of cases of ovarian cancer were highest in women who had never used hormonal contraception — 7.5 per 100,000 person years). Among women who had ever used hormonal contraception, the number of cases of ovarian cancer were 3.2 per 100,000 person years.
There was no firm evidence to suggest any protective effect among women who used progestogen-only products, although the researchers point out that few women were exclusive users of these products.
The reduced risk for combined products was seen with nearly all types of ovarian cancer, and there was little evidence of important differences between products containing different types of progestogens. Similar results were also found among women followed up to their first switch in contraceptive type.
Based on these figures, researchers said that hormonal contraception prevented an estimated 21 per cent of ovarian cancers in this group of women.