Breast cancer diagnosis is higher among women who currently use or recently used contemporary hormonal contraceptives than among women who have never used hormonal contraceptives, and this risk increased with longer durations of use, according to a study published in the New England Journal of Medicine.
The research team, led by Lina S. Mørch, PhD, from the Department of Gynecology at the University of Copenhagen, conducted a nationwide prospective cohort study including all women in Denmark between the ages of 15 and 49 years who were not diagnosed with cancer or venous thromboembolism and who never received treatment for infertility. Use of hormonal contraceptives was categorized as current use or recent use (discontinuation within the previous 6 months) or previous use (discontinuation ≥6 months previously). Start of use was the date that the prescription was purchased, and the Danish Cancer Registry was used to identify primary invasive breast cancers.
From January 1, 1995, through December 31, 2012, with a mean follow-up of 10.9 years, a total of 19.6 million person-years and 11,517 incident breast cancer diagnoses occurred in 1,797,932 women between the ages of 15 and 49 years. As compared with women who had never used hormonal contraception, the relative risk [RR] of breast cancer among all current and recent users of hormonal contraception was 1.20 (95% confidence interval [CI]). The risk of breast cancer increased with the duration of use, from 1.09 with ≤1 year of use to 1.38 after ≥10 years of use. After discontinuation of hormonal contraception, the risk of breast cancer was still higher among the women who had used hormonal contraceptives for ≥5 years than among women who had not used hormonal contraceptives.
Risk estimates associated with current or recent use of various oral combination (estrogen-progestin) contraceptives varied between 1.0 and 1.6. Women who currently use or recently used the progestin-only intrauterine device (IUD) also had a higher risk of breast cancer than women who had never used hormonal contraceptives (RR, 1.21). The overall absolute increase in breast cancers diagnosed among current and recent users of any hormonal contraceptive was 13 per 100,000 person-years, or approximately 1 extra breast cancer for every 7,690 women using hormonal contraception for 1 year.
“In this prospective cohort study, the current or recent use of hormonal contraception was associated with a higher risk of breast cancer than the risk among women who had never used hormonal contraceptives, with little evidence of major differences between specific combined oral contraceptives,” the authors concluded. “The risk increased with the duration of use.”
Mørch LS, Skovlund CW, Hannaford PC, et al. Contemporary hormonal contraception and the risk of breast cancer. N Engl J Med. 2017 Dec 7;377(23). doi: 10.1056/NEJMoa1700732