Morch LS, et al. - The tie-up between the use of hormonal contraception and the risk of invasive breast cancer was exploratively analyzed in this study. Findings unveiled higher risk of breast cancer among women who currently or recently used contemporary hormonal contraceptives than among women who had never used hormonal contraceptives. A rise was noted in this risk with longer durations of use. Nevertheless, absolute increases in risk were discovered to be minor.

Methods

• The correlations between the use of hormonal contraception and the risk of invasive breast cancer were contemplated by the authors.
• This nationwide prospective cohort study examined all women in Denmark between 15 and 49 years of age who had not had cancer or venous thromboembolism and who had not received treatment for infertility.
• Individually updated information was obtained via nationwide registries regarding the use of hormonal contraception, breast-cancer diagnoses, and potential confounders.

Results

• A total of 1.8 million women were followed on average for 10.9 years (a total of 19.6 million person-years).
• The occurrence of breast cancer was noted in 11,517 cases.
• The relative risk of breast cancer among all current and recent users of hormonal contraception was discovered to be 1.20 (95% confidence interval [CI], 1.14 to 1.26) when compared to women who had never used hormonal contraception.
• A rise was noted in the risk from 1.09 (95% CI, 0.96 to 1.23) with less than 1 year of use to 1.38 (95% CI, 1.26 to 1.51) with more than 10 years of use (P=0.002).
• The risk of breast cancer remained higher among the women who had used hormonal contraceptives for 5 years or more, following the discontinuation of hormonal contraception, than among women who had not used hormonal contraceptives.
• Variation was illustrated in the risk estimates related to current or recent use of various oral combination (estrogen-progestin) contraceptives between 1.0 and 1.6.
• A higher risk of breast cancer was experienced in women who currently or recently used the progestin-only intrauterine system also than women who had never used hormonal contraceptives (relative risk, 1.21; 95% CI, 1.11 to 1.33).
• It was noted that the overall absolute increase in breast cancers diagnosed among current and recent users of any hormonal contraceptive was 13 (95% CI, 10 to 16) per 100,000 person-years, or approximately 1 extra breast cancer for every 7,690 women using hormonal contraception for 1 year.