medwireNews: Women using contemporary combined oral contraceptives containing newer progestogens have a reduced risk for ovarian cancer compared with women not using hormonal contraception, a nationwide cohort study shows.
Among women who had used hormonal contraceptives of any type, either in the past or currently, the reduction in the age standardized absolute rate of ovarian cancer was 3.2 per 100,000 person–years, the researchers report. This compared with 7.5 per 100,000 person–years among women who had never used hormonal contraception.
This gave a significant overall relative risk reduction in ovarian cancer of 34% with hormonal contraceptive use over no use, with significant reduced risk estimates for current or recent use as well as former use, at 42% and 23%.
Most hormonal contraceptives used by the 1,879,227 women participating in the study were combined oral contraceptives, at 86%, and “[t]here was little evidence of important differences between combined oral contraceptives containing different types of progestogens,” note Lisa Iversen (University of Aberdeen, UK) and colleagues.
There was no evidence of a protective effect with progestogen-only products, however. But the investigators point out that too few women were exclusively using this type of contraceptive to be able to accurately detect such an effect.
The protection offered by hormonal contraceptive use “strengthened with longer periods of current use and persisted for several years after stopping use,” the team reports in The BMJ. The relative risk reduction in ovarian cancer was 38% within 1 to 5 years of use and increased to 74% with more than 10 years of use.
The reduction in risk diminished with time since stopping use, from 24% in women who last used hormonal contraceptives up to 5 years ago to 20% in those who had stopped more than 10 years ago, at which point the reduction in risk was no longer significant.
“When both time since last use and duration were examined, evidence among former users of any hormonal contraception indicated greater protection with longer durations of use and a suggestion that the protection waned more quickly in those with shorter duration of use,” the researchers comment.
The study included women aged 15 to 49 years, limiting the number who would be using hormone replacement therapy, which is known to increase ovarian cancer risk.
“While this age restriction meant that we could be confident that we were examining the effects of oral contraception, it also meant that the study could not provide information on how contemporary hormonal contraceptives affected ovarian cancer risk in older women, in whom most cases of ovarian cancer occur,” Iversen and colleagues acknowledge.
They conclude that “contemporary combined hormonal contraceptives are still associated with a reduced risk of ovarian cancer in women of reproductive age, with patterns similar to those seen with older combined oral products.”
By Lucy Piper
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