UPA effects on endometrium - what is the significance?

Introduction: Selective progesterone receptor modulators (SPRMs), such as Mifepristone, Asoprisnil, Ulipristal acetate (UPA) and Vilaprisan, were tested for their antiproliferative effects on uterine fibroids. In Romania, despite the UPA availability, physicians remained reserved on the lack of experience and concerns about the safety of the drug on endometrium.
Patients, Materials and Methods: We performed an observational study on premenopausal women with symptomatic uterine fibroids. The patients received UPA in doses of 5 mg for 12-13 weeks. The fibroids dimensions and endometrium thickness were recorded at before and after the treatment. The pathological samples were assessed by two pathologists, and they recorded progesterone receptor modulator associated endometrial changes (PAEC) as extensive PAEC (EPAEC), minimally PAEC (MPAEC), absent PAEC (APAEC) and Ki67 immunoexpression in endometrium.
Results: A number of 57 women were introduced in our study and we had a dropout of one patient. The fibroid dimensions and endometrial thickness decreased after UPA. The pathological exam of the endometrium revealed: APAEC in 26.8% of cases, MPAEC in 60.7% of cases and EPAEC in 12.5% of cases. EPAEC were more frequent in patients with larger fibroids. PAEC had a strong correlation with Ki67 index (p≤0.01). PAEC were more frequent in older women (p≤0.01). Ki67 had a higher expression in EPAEC - mean: 69% (range: 63-75%), standard deviation (SD): 3.95.
Conclusions: UPA treatment decreased fibroids dimension and improved patients' symptoms in our study. EPAEC was associated with abundant Ki67 antigen. UPA administration for three months is a safe method without endometrial atypia but longer protocols require extended studies about the proliferative potential of the endometrium.