Does Dienogest Increase the Risk of Breast Cancer?
Many patients with endometriosis ask during clinic visits:
“Will taking this medication cause breast cancer?”
This is a very good question and definitely worth discussing.
What does the latest research say?
A nationwide cohort study from Korea in 2025 analyzed more than 100,000 women aged 20–49.
All of these women had endometriosis and had used Dienogest continuously for at least six months.
The results showed that:
The incidence of breast cancer in the Dienogest group was the same as in the group receiving GnRH injections, with no significant difference.
The adjusted hazard ratio, aHR, was 1.01, with a 95% CI of 0.75–1.37.
Interestingly, short-term use, from 0.5 to 1.5 years, was associated with an even lower risk.
The aHR was 0.72, with a 95% CI of 0.53–0.99.
However, whether long-term use changes the risk still requires longer follow-up.
So why are people concerned?
Earlier cell studies found that in certain breast cancer cell lines, especially those with high PGRMC1 expression, Dienogest might promote cell proliferation.
However, that was a finding at the in vitro cellular level.
Clinically, there is currently no evidence showing an increased incidence of breast cancer because of Dienogest.
Clinical conclusion
The safety profile of Dienogest currently appears quite stable.
Its breast cancer risk is comparable to that of GnRH agonist medications, and there is no clinical evidence showing an increased risk of breast cancer.
✅ Suitable for patients who need long-term control of endometriosis
✅ If you have a family history of breast cancer or a BRCA gene mutation, it is still recommended to discuss this with your doctor and receive regular follow-up
Dr. Li’s reminder
The key to treating endometriosis is to find a method that can provide stable long-term control, rather than simply fearing medication.
True risk management means regular follow-up and being honest with your body.
References:
1️⃣ Jhang H et al., Int J Gynaecol Obstet, 2025; doi:10.1002/ijgo.70424.
2️⃣ Schneck H et al., Gynecol Endocrinol, 2013;29(2):160–3.
Yun-I wishes your dreams come true!
