Oral contraceptives are not associated with a long-term cancer risk and may be protective against some forms of cancer, according to a study published in the American Journal of Obstetrics & Gynecology.
Lisa Iversen, PhD, from the Institute of Applied Health Sciences at the University of Aberdeen in the United Kingdom, and colleagues, examined the very long-term cancer risks or benefits associated with the use of combined oral contraceptives, including the estimated overall lifetime balance. A total of 46,022 women were recruited to the UK Royal College of General Practitioners’ Oral Contraception Study from 1968 and 1969 and were observed for up to 44 years. Women were grouped into “ever” and “never” users of oral contraceptives, and data were standardized for age, parity, social class, and smoking.
A total of 4661 “ever” users developed at least 1 cancer during 884,895 woman-years of observation and 2341 “never” users developed at least 1 cancer during 388,505 woman-years of observation. Ever use of oral contraceptives was associated with reduced colorectal, endometrial, ovarian, and lymphatic and hematopoietic cancers (0.81, 0.66, 0.67, 0.74 incidence rate ratios, respectively).
An increased risk of lung cancer was only observed among smokers. An increased risk of breast and cervical cancer that was seen in current and recent users appeared to decrease within approximately 5 years of stopping contraception, with no evidence of either cancer recurring. There was no evidence of new cancer risks appearing later in life among women who had used oral contraceptives.
“The overall balance of cancer risk among past users of oral contraceptives was neutral with the increased risks counterbalanced by the endometrial, ovarian, and colorectal cancer benefits that persist at least 30 years,” the authors said.
- Iversen L, Sivasubramaniam S, Lee AJ, et al. Lifetime cancer risk and combined oral contraceptives: the Royal College of General Practitioners’ Oral Contraception Study. Am J Obstet Gynecol. 8 February 2017. doi: 10.1016/j.ajog.2017.02.002