By Bianca Nogrady
Hormonal contraceptive use is associated with a reduced risk of ovarian cancer, according to a Danish nationwide cohort study.
Writing in the BMJ, researchers presented the results of their prospective study including about 1.9 million women, 1249 of whom were diagnosed with ovarian cancer, and 13,344,531 person-years of follow up. They found that women who were currently using or had recently used hormonal contraception had a 42% lower relative risk of ovarian cancer compared with never users.
The relative risk of ovarian cancer decreased with increasing duration of hormonal contraceptive use; it was 84% lower in women who had used hormonal contraception for more than 10 years.
Women who had formerly used hormonal contraception had a 23% lower relative risk of ovarian cancer.
Although progestogen-only contraceptives were not associated with a reduced risk of ovarian cancer, the authors noted that there were relatively few women exclusively using progestogen-only products, so the analysis had limited statistical power.
Commenting on the study, Clinical Associate Professor Deborah Bateson said the findings were reassuring for women using hormonal contraception.
‘It includes women who are using contemporary pills with lower oestrogen doses, newer progestogens as well as extended or continuous regimens with fewer hormone-free breaks,’ said Professor Bateson, Medical Director of Family Planning NSW.
‘While we often hear about the risks of hormonal contraception it’s good to now have positive news to support women in making an informed decision about which contraceptive method to choose – one that is based on the benefits as well as the risks.’
Professor Bateson noted that the study did not provide evidence of causality in relation to the protective effect of combined hormonal contraception. Although the exact mechanism is unclear, the association with reduced ovarian cancer risk may reflect suppression of ovulation and a reduced number of ovulatory cycles.
‘In times gone by women used to have far fewer ovulations because of multiple pregnancies and breastfeeding for long periods of time,’ she said. ‘Whereas today’s contemporary women have potentially far more ovulations during their lifetime unless they are using a method of contraception such as the combined pill.’
BMJ 2018; 362: K3609.