A recent study set out to determine if the association between oral contraceptives and the risk of particular cancers was affected by lifestyle factors.
Oral contraceptives are commonly used and there is substantial research on the risks and benefits regarding their use.
A study carried out in the United States and published in JAMA Oncology investigated if the link between the duration of oral contraceptive use and the risk of specific cancers was modified by lifestyle factors such as smoking, obesity, and exercise.
The population-based cohort study included over 100,000 women and observed a decreased risk for ovarian cancer associated with an increased use of oral contraceptives.
This pattern was observed fairly consistently across health behaviors.
Interestingly, for endometrial cancer, the risk reduction was strongest for current smokers, obese women, and those who exercised infrequently. There was a lack of association between oral contraceptives and breast and colorectal cancer risk, which was consistent across health behaviors.
The main limitation of this study is that it did not adjust for certain mediators that could provide a causal path between oral contraceptive use and cancer risk.
This prevented the use of mediation methods that can provide an element of control for confounding factors such as parity. However, the conclusions of this study are consistent with many other studies that did adjust for factors such as parity.
This recent study has investigated if the link between the duration of oral contraceptive use and the risk of specific cancers was modified by lifestyle factors and has thus concluded that the favorable effects of oral contraceptive use on ovarian and endometrial cancer risk are observed across most lifestyle factors such as smoking and obesity.
However, it is important to highlight that the investigators of this study did not obtain information on the formulation of the oral contraceptives used.
The women within this study were likely using first and second-generation contraceptive drugs; those marketed before 1989.
These older contraceptive drugs contained higher levels of hormones than the newer oral contraceptive drugs used today. Despite the positive results of this study, the researchers acknowledge the need for future studies that investigate the newer oral contraceptive drugs and the associations between their use and cancer risks across various health behaviors.
This study adds to the existing literature surrounding oral contraceptive use and cancer risk and thus provides further information to allow clinicians to advise their patients regarding the risks and benefits of taking oral contraception.
Written by Jade Marie Evans, MPharm, Medical Writer
Reference: Michels K.A et al. (2018). Modification of the Associations Between Duration of Oral Contraceptive Use and Ovarian, Endometrial, Breast, and Colorectal Cancers. Available: https://jamanetwork.com/journals/jamaoncology/article-abstract/2669779?resultClick=1&redirect=true. Last accessed 1st February 2018