Contemporary Hormonal Contraception and the Risk of Breast Cancer

TY - JOUR

T1 - Contemporary Hormonal Contraception and the Risk of Breast Cancer

AU - Mørch, Lina S

AU - Skovlund, Charlotte W

AU - Hannaford, Philip C

AU - Iversen, Lisa

AU - Fielding, Shona

AU - Lidegaard, Øjvind

PY - 2017/12/7

Y1 - 2017/12/7

N2 - BACKGROUND Little is known about whether contemporary hormonal contraception is associated with an increased risk of breast cancer. METHODS We assessed associations between the use of hormonal contraception and the risk of invasive breast cancer in a nationwide prospective cohort study involving 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. Nationwide registries provided individually updated information about the use of hormonal contraception, breast-cancer diagnoses, and potential confounders. RESULTS Among 1.8 million women who were followed on average for 10.9 years (a total of 19.6 million person-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 users of hormonal contraception was 1.20 (95% confidence interval [CI], 1.14 to 1.26). This risk increased 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). After discontinuation of hormonal contraception, the risk of breast cancer was still higher among the women who had used hormonal contraceptives for 5 years or more 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 or recently used the progestin-only intrauterine system also had a higher risk of breast cancer than women who had never used hormonal contraceptives (relative risk, 1.21; 95% CI, 1.11 to 1.33). 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 personyears, or approximately 1 extra breast cancer for every 7690 women using hormonal contraception for 1 year. CONCLUSIONS 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.

AB - BACKGROUND Little is known about whether contemporary hormonal contraception is associated with an increased risk of breast cancer. METHODS We assessed associations between the use of hormonal contraception and the risk of invasive breast cancer in a nationwide prospective cohort study involving 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. Nationwide registries provided individually updated information about the use of hormonal contraception, breast-cancer diagnoses, and potential confounders. RESULTS Among 1.8 million women who were followed on average for 10.9 years (a total of 19.6 million person-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 users of hormonal contraception was 1.20 (95% confidence interval [CI], 1.14 to 1.26). This risk increased 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). After discontinuation of hormonal contraception, the risk of breast cancer was still higher among the women who had used hormonal contraceptives for 5 years or more 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 or recently used the progestin-only intrauterine system also had a higher risk of breast cancer than women who had never used hormonal contraceptives (relative risk, 1.21; 95% CI, 1.11 to 1.33). 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 personyears, or approximately 1 extra breast cancer for every 7690 women using hormonal contraception for 1 year. CONCLUSIONS 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.

KW - Adolescent

KW - Adult

KW - Age Distribution

KW - Breast Neoplasms/chemically induced

KW - Contraceptives, Oral, Hormonal/adverse effects

KW - Denmark/epidemiology

KW - Estradiol/adverse effects

KW - Estrogens/adverse effects

KW - Female

KW - Humans

KW - Intrauterine Devices, Medicated/adverse effects

KW - Progestins/adverse effects

KW - Prospective Studies

KW - Registries

KW - Risk

KW - Risk Assessment

KW - Time Factors

KW - Young Adult

U2 - 10.1056/nejmoa1700732

DO - 10.1056/nejmoa1700732

M3 - Journal article

C2 - 29211679

SN - 0028-4793

VL - 377

SP - 2228

EP - 2239

JO - The New England Journal of Medicine

JF - The New England Journal of Medicine

IS - 23

ER -