Endometrial safety of an oral contraceptive containing estradiol valerate and dienogest

BACKGROUND The purpose of this study was to investigate the endometrial safety of an oral contraceptive containing estradiol valerate/dienogest (E(2)V/DNG) administered as an estrogen step-down and progestogen step-up regimen in women of reproductive age (18-50 years), using histological assessment of endometrial biopsy samples. METHODS Endometrial biopsies were taken in a subset of healthy women who took part in a multicenter, open-label, noncomparative study assessing the contraceptive efficacy and safety of an E(2)V/DNG oral contraceptive. In each 28-day cycle, women received E(2)V 3 mg on days 1-2, E(2)V 2 mg/DNG 2 mg on days 3-7, E(2)V 2 mg/DNG 3 mg on days 8-24, E(2)V 1 mg on days 25-26, and placebo on days 27-28. Women underwent endometrial biopsy between days 12 and 19 of the cycle, both at screening and at cycle 20 (or at the final examination). RESULTS Of the 283 women who underwent an endometrial biopsy at screening, 218 underwent a follow-up biopsy at cycle 20. At screening, abnormal biopsy results, both classified as "simple hyperplasia without atypia", were seen in two women, who were withdrawn from the trial. At cycle 20, there were no abnormal findings of endometrial hyperplasia or malignancy, and 80.9% of women had atrophic, inactive, or secretory endometrium. CONCLUSION After 20 cycles of treatment, an oral contraceptive containing E(2)V and DNG is safe and effective to transform the endometrium into a secretory/inactive or atrophic status, and exhibits no deleterious effects on endometrial histology in women aged 18-50 years.