Use of new types of combined oral contraceptives (containing both lower doses of estrogens and newer progestogens) is associated with a reduction in the risk of ovarian cancer among young women, finds a new study published in The BMJ.
The results show that this positive effect strengthened with longer periods of use and persisted for several years after stopping, providing important reassurance for women, say the researchers.
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 estrogen 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.
So, Lisa Iversen, research fellow, Academic Primary Care, Institute of Applied Health Sciences, University of Aberdeen, Aberdeen, UK, and colleagues conducted the study to investigate the association between contemporary combined hormonal contraceptives and overall and specific types of ovarian cancer.
For the study, the researchers analyzed data for nearly 1.9 million Danish women aged 15-49 years between 1995 and 2014 using prescribing and cancer registers. Women were categorized as never users (no record of being dispensed hormonal contraception), 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%) of the hormonal contraceptive use related to combined oral products.
- The number of cases of ovarian cancer was highest in women who had never used hormonal contraception (7.5 per 100,000 person-years), whereas, among women who had ever used hormonal contraception, the number of cases of ovarian cancer was 3.2 per 100,000 person-years.
- Relative risks among current or recent users decreased with increasing duration (from 0.82 (0.59 to 1.12) with ≤1 year use to 0.26 (0.16 to 0.43) with >10 years’ use). Similar results were achieved among women followed up to their first switch in the contraceptive type
- Little evidence of major differences in risk estimates by tumor type or progestogen content of combined oral contraceptives was seen.
- Use of progestogen-only products was not associated with ovarian cancer risk.
- Among ever users of hormonal contraception, the reduction in the age-standardized absolute rate of ovarian cancer was 3.2 per 100 000 person-years.
- Based on the relative risk for the never use versus ever use categories of hormonal contraception (0.66), the population prevented fraction was estimated to be 21%—that is, use of hormonal contraception prevented 21% of ovarian cancers in the study population.
This is an observational study, so no firm conclusions can be drawn about cause and effect, but they do support the findings of studies of older products. The researchers point out that they did not study older women, among whom most cases of ovarian cancer occur. However, this was a large study with a long follow-up period, and the researchers were able to adjust for a range of potentially influential factors.
“Based on our results, 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,” say the authors.
“The reduced risk seems to persist after stopping use, although the duration of benefit is uncertain. Presently, there is insufficient evidence to suggest similar protection among exclusive users of progestogen-only products. These data suggest no protective effect from progestogen-only products,” they conclude.
For further reference follow the link: https://doi.org/10.1136/bmj.k3609