INTRODUCTION:
Breast cancer survivors are advised to avoid hormone use for contraception or peri-menopausal or post-menopausal symptoms. This study assessed the recurrence and mortality risks of contraceptive and non-contraceptive hormone use in breast cancer survivors.
METHODS:
We retrospectively studied women aged 18-55 years who were diagnosed with stage I-III breast cancer during 2006-2015 and entered remission. Multivariable extended proportional hazards models, supporting adjusted hazard ratio (HR), overall survival (OS), and locoregional and distant recurrence probability estimation, were used to examine the time-dependent effects of hormonal contraception (pill, patch, ring, subcutaneous device, injection, intrauterine device) and non-contraceptive hormonal therapies (e.g., menopausal symptoms), while adjusting for time-invariant patient, tumor, and treatment effects.
RESULTS:
Following diagnosis, 3,134 (91.2%) patients used no hormones, 171 (4.98%) used hormonal contraceptives, 129 (3.75%) used non-contraceptive hormones, and 3 (0.09%) used both. Models incorporating patients who used hormonal contraceptives versus no hormones revealed recurrence risk did not differ between groups (HR: 0.78, 95% confidence interval [CI]: 0.34-1.80). Mortality risk also did not differ (HR: 0.52, 95% CI: 0.13-2.15), with 5-year OS rates of 0.97 (95% CI: 0.90-0.99) and 0.95 (95% CI: 0.94-0.96), respectively. In models incorporating patients who used non-contraceptive hormones versus no hormones, recurrence risk was similar (HR: 1.52, 95% CI: 0.77-2.99) but hormone users incurred greater risk of death (HR: 2.95, 95% CI: 1.70-5.09).
CONCLUSION:
Breast cancer survivors who use hormonal contraceptives are not at increased risk of recurrence or mortality relative to women who do not use hormones. However, those who use non-contraceptive hormones demonstrate greater mortality risk.
