Women who currently or recently used contemporary hormonal contraceptives have a higher risk of breast cancer compared to women who had never used hormonal contraceptives, and this risk increased with longer durations of use. This according to a nationwide prospective cohort study involving all women aged 15 to 49 years who had not had cancer or venous thromboembolism and who had not received treatment for infertility. Researchers found:
- Among 1.8 million women followed on average for 11 years, 11,517 cases of breast cancer occurred.
- As compared with women who had never used hormonal contraception, the relative risk of breast cancer among all current and recent user of hormonal contraception was 1.20.
- This risk increased from 1.09 with <1 year of use to 1.38 with >10 years of use.
- After discontinuation of hormonal contraception, the risk of breast cancer was still higher among women who had used hormonal contraceptives for ≥5 years than among women who had not used hormonal contraceptives.
Mørch LS, Skovlund CW, Hannaford PC, Iversen L, Fielding S, Lidegaard Ø. Contemporary hormonal contraception and the risk of breast cancer. N Engl J Med. 2017;377:2228-2239. doi:10.1056/NEJMoa1700732.
This is an article for which it is important to understand the details, not just the headline results. It is important to understand that while the relative risk was 20% higher for all women both above and below 35 years of age, the absolute increase in risk of breast cancer was very different for older vs younger women. Because the incidence of breast cancer increases a great deal the older women get, particularly above age 40, a 20% increase in risk has a much larger impact for women over age 40 than for those younger than 35. The meaning of this is discussed in the accompanying editorial, which clarifies that “the absolute increase in risk is 13 per 100,000 women overall, but only 2 per 100,000 women younger than 35 years of age; most of the cases that occurred in this analysis occurred among women who were using oral contraceptives in their 40.”1 What this tells us is that this increased risk becomes a more important issue for women over age 40, in whom the absolute likelihood of developing breast cancer increases dramatically compared to younger women. —Neil Skolnik, MD
- Hunter DJ. Oral contraceptives and the small increased risk of breast cancer. N Engl J Med. 2017;377:2276-2277. doi:10.1056/NEJMe1709636.
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