Posted on January 18, 2018
Oral contraceptives have been widely used by U.S. women for over 50 years. In addition to preventing pregnancy, these medications have been shown to either increase or decrease a woman’s risk of developing certain cancers, though the reasons why are not fully understood. Notably, many questions remain around how oral contraceptive use affects cancer risk in subpopulations of women, such as smokers and overweight women. These groups are already at higher risk for many cancers, so it is especially important to understand how oral contraceptive use changes cancer risks in these women. To address this gap, DCEG researchers investigated whether the relationship between oral contraceptive use and risks for ovarian, endometrial, breast, and colorectal cancers change when looking at groups of women who have different health behaviors in the years leading up to and during menopause (for example, smoking, alcohol use, BMI, and physical activity). The findings were published on January 18, 2018 in JAMA Oncology.
Analyzing data from nearly 200,000 women from the NIH-AARP Diet and Health Study, Kara Michels, Ph.D., Britton Trabert, Ph.D., M.S., and colleagues found that long-term oral contraceptive use (10 years or longer) was associated with reduced risk for ovarian cancer regardless of other health behaviors in later life. Long term oral contraceptive use also reduced risks for endometrial cancer, but this reduction was strongest for women who were current smokers, obese, or rarely exercised.
Oral contraceptive use was generally not associated with either colorectal cancer or breast cancer.
Previous studies have reported that current or recent use of oral contraceptives may slightly increase breast cancer risk. However, the NIH-AARP Diet and Health Study enrolled women who were between 50 and 71 years of age, most of whom were neither current nor recent users of oral contraceptives.
In the future, these findings should be replicated in other populations, particularly among a more diverse group of women. Research to evaluate risks among users of contemporary oral contraceptive medications is also needed. The medications prescribed today are different from those available between the 1960s and 1980s, when most of the study participants would have taken them.
The authors note that the results of this analysis indicate that oral contraceptive use may be beneficial for cancer prevention for a range of women with different underlying cancer risk.
Reference: Michels et al. Modification of the associations between duration of oral contraceptive use and ovarian, endometrial, breast, and colorectal cancers. January 18, 2017. JAMA Oncology. DOI:10.1001/jamaoncol.2017.4942