As reported in The New England Journal of Medicine by Lina S. Mørch, PhD, of the University of Copenhagen, and colleagues, a Danish study has shown that the risk of breast cancer is increased in hormonal contraception users vs nonusers, with the absolute increase in risk being small.
The study assessed the association between the use of hormonal contraception and the risk of invasive breast cancer among all women in Denmark aged 15 to 49 years as of January 1, 1995, and those who subsequently were aged 15 years before December 31, 2012, who had not had cancer or venous thromboembolism and who had not received treatment for infertility.
Increased Cancer Risk
Among 1.8 million women with an average follow-up of 10.9 years (19.6 million person-years), 11,517 cases of breast cancer were identified. The relative risk for breast cancer was 1.20 (95% confidence interval [CI] = 1.14–1.26) for current and recent (discontinuation within the prior 6 months) users of hormonal contraception vs never-users, with the relative risk increasing from 1.09 (95% CI = 0.96–1.23) for < 1 year of use to 1.38 (95% CI = 1.26–1.51) for > 10 years of use (P = .002). The risk remained elevated compared with never-users for women discontinuing hormonal contraception after ≥ 5 years of use but not among those discontinuing use after < 5 years. Relative risk estimates for current or recent use of different oral combination (estrogen-progestin) contraceptives ranged from 1.0 to 1.6 vs never-use. The absolute increase in risk associated with current/recent use vs never-use was 13 cases per 100,000 person-years, corresponding to approximately 1 extra case of breast cancer for every 7,690 women using hormonal contraception for 1 year.
The investigators concluded: “The risk of breast cancer was higher among women who currently or recently used contemporary hormonal contraceptives than among women who had never used hormonal contraceptives, and this risk increased with longer durations of use; however, absolute increases in risk were small.” ■