Results of this study showed positive effects were strengthened with longer periods of use and even persisted several years after stopping, according to the researchers of this large study from the University of Aberdeen and the University of Copenhagen.
It is estimated that 100 million women are using hormonal contraception every day around the globe. Reduced risk of ovarian cancer in women taking combined oral contraceptives has been shown in previous studies, but most evidence relates to older products containing higher levels of oestrogen and older progestogens. This study was conducted to investigate if the same can be said for those who use newer forms of oral contraceptives and other hormonal contraceptive methods on overall and specific types of ovarian cancer in women of reproductive age.
Data was analysed for nearly 1.9 million Danish women between the ages of 15-49 using the national prescribing and cancer registers. Subjects were categorised as: never users having no record of being dispensed hormonal contraception; current or recent user up to one year of stopping use; or former users having stopped for more than one year of different hormonal contraceptives. 86% of the hormonal contraceptive use was found to be related to combined oral products.
The number of cases for ovarian cancer were found to be highest in those who had never used hormonal contraception after taking into account several factors including age and parity. No firm evidence was found to suggest any protective effect among those who used progestogen only products. Reduced risk for combined products was seen in nearly all types of ovarian cancer with little evidence of important differences between products containing different types of progestogens. Similar results were found for those who switched from their first older contraceptive type to newer.
Based on their findings the researchers suggest that hormonal contraception prevented an estimated 21% of ovarian cancers in this study group. As this is an observational study no firm conclusions can be made as to cause and effect. Limitations include the nature of the observational study, and that older women were not included in the study among whom most cases of ovarian cancer occur. Researchers explain as this was a large study that included a long follow up period they were able to adjust for a range of potentially influential factors, and were confident of their findings of contemporary combined hormonal contraceptives still being associated with reduced risk of ovarian cancer in those of reproductive age, and the protection seems to persist after stopping use. Presently there is not enough evidence to determine the duration of benefit persisting after use has stopped, and there is insufficient evidence to suggest similar protection among exclusive use of progestogen only products.
