Chemoprevention With Oral Contraceptives Could Be a Reality

Evidence provided by a study published in The Lancet Oncology affirms that oral contraceptives provide long-term protection against endometrial cancer. The authors estimate that about 400,000 cases of endometrial cancer in those 75 years or younger may have been prevented in developed nations—as a result of oral contraception—during the period between 1965 and 2014, and 50% in the last decade.

The incidence of endometrial cancer is rare in women younger than 45 years of age and the risk of disease increases in women 55 years and older.

The researchers of the Lancet study combined data on 27,276 women with endometrial cancer from 36 epidemiological studies from North America, Europe, Asia, Australia, and South Africa. The median age of the women in the study was 63 years and the median year of diagnosis was 2001. While 35% of the 27,276 cases reported using oral contraception for a media of 3 years, 39% of the more than 115,500 controls had used oral contraceptives for a median duration of 4.4 years.

The analysis revealed that every 5 years of oral contraceptive use reduced the risk of endometrial cancer by about a quarter, and the reduction of risk persisted for more than 30 years after the women had stopped using the contraceptive agent. In high-income countries, 10 years of oral contraceptive use reduces the risk of developing endometrial cancer before age 75 years from 2.3 to 1.3 cases per 100 users, the authors found. However, the risk reduction varied by tumor type—it was stronger for carcinomas than sarcomas.

Considering that estrogen levels in pills in the early decades were double those in contraceptive pills manufactured today, the reduction in risk was comparable, which suggests that the amount of hormones in the lower-dose pills is still sufficient to reduce the incidence of endometrial cancer, according to the authors.

The proportional risk reduction did not vary substantially by women’s reproductive history, adiposity (amount of body fat), alcohol use, tobacco use, or ethnicity.

“The strong protective effect of oral contraceptives against endometrial cancer—which persists for decades after stopping the pill—means that women who use it when they are in their 20s or even younger continue to benefit into their 50s and older, when cancer becomes more common,” explained study author professor Valerie Beral, from the University of Oxford in a press release.

She added “Previous research has shown that the pill also protects against ovarian cancer. People used to worry that the pill might cause cancer, but in the long term the pill reduces the risk of getting cancer.”

The American Cancer Society estimates that more than 10,000 women will die of uterine cancers in the United States in 2015. So what do the results of this retrospective study mean?

In an accompanying commentary in the journal, Nicolas Wentzensen and Amy Berrington de Gonzalez from the Division of Cancer Epidemiology and Genetics at the National Institutes of Health in the United States discuss other ongoing studies examining the use of oral contraceptives as chemoprevention in women carrying BRCA1 and BRCA2 mutations and against Lynch syndrome. “Even if the biological mechanisms remain elusive and the existing evidence falls short of wider recommendations for chemoprevention, women need to be more aware of the unintended benefits and the risks of oral contraceptives, so that they can make informed decisions,” they write.