Dienogest use and the risk of breast and gynecologic cancers: A nationwide population‐based study
Abstract
Objective
To evaluate whether dienogest exposure is associated with the risk of breast, endometrial, or tubo‐ovarian cancer in women with endometriosis.
Methods
In this nationwide retrospective cohort study (January 2012 to December 2023), we used the Korean National Health Insurance Review & Assessment Service database. Women aged 20–49 years with endometriosis who received dienogest for at least 6 months were compared with an active control group treated with gonadotropin‐releasing hormone (GnRH) agonists, with cohorts balanced by inverse probability of treatment weighting. Incident breast, endometrial, and tubo‐ovarian cancers were ascertained, and adjusted hazard ratios (aHR) were estimated using Cox proportional hazards models.
Results
Among 1 887 957 women with endometriosis, 14 647 dienogest users and 181 587 GnRH agonist users met the eligibility criteria for the breast cancer cohort; sample sizes were similar for endometrial and tubo‐ovarian analyses. Compared with GnRH agonists, dienogest use was not associated with increased risk of breast cancer (aHR 1.01, 95% confidence interval [CI] 0.75–1.37), endometrial cancer (aHR 0.84, 95% CI 0.40–1.77), or tubo‐ovarian cancer (aHR 0.92, 95% CI 0.30–2.80). Use of dienogest for 0.5–1.5 years was associated with a reduced breast cancer risk (aHR 0.72, 95% CI 0.53–0.99), whereas associations for longer durations were inconsistent.
Conclusion
Dienogest use in women with endometriosis was not associated with higher or lower risks of breast, endometrial, or tubo‐ovarian cancer compared with GnRH agonists, supporting its oncologic safety. Further longer‐term studies are warranted to clarify duration‐specific effects.