Objective: To evaluate the endometrial hyperplasia and carcinoma rate after 52-week treatment with ultra-low-dose 10-microgram 17β-estradiol vaginal tablets in postmenopausal women with vaginal atrophy.
Methods: Endometrial biopsy data from individuals using active treatment (n=205) in a randomized, double-blind, placebo-controlled trial were pooled with the data from an open-label endometrial safety trial (n=336). Patients received 10-microgram estradiol vaginal tablets for 52 weeks. All endometrial biopsy samples were histologically analyzed at baseline and at end of trial by the same laboratory in both trials.
Results: A total of 541 women using estradiol were included in the combined analysis of endometrial safety. A total of 456 women completed the trials, and 443 women had a biopsy performed at week 52: 85.6% were categorized as "atrophic endometrium," 12.6% had nonevaluable biopsy samples, 1.1% had polyps, and 0.2% were categorized as "weakly proliferative." One case of complex hyperplasia without atypia was reported in an individual exposed to trial drug for only 9 days. One woman's biopsy sample demonstrated endometrioid adenocarcinoma, grade 2, but the lack of an evaluable screening biopsy sample makes it uncertain whether the carcinoma was preexisting. In total, two events of hyperplasia and carcinoma were reported in 386 evaluable biopsy samples (incidence rate 0.52% per year).
Conclusion: The reported background incidence rate of endometrial hyperplasia and carcinoma in postmenopausal women is 0% to 1%. The results of this pooled analysis therefore support the endometrial safety of unopposed ultra-low-dose vaginal estrogen. There was no increased risk of endometrial hyperplasia and carcinoma in postmenopausal women undergoing treatment with 10-microgram estradiol vaginal tablets for 1 year under study conditions.
Clinical trial registration: ClinicalTrials.gov, www.clinicaltrials.gov, NCT00108849 (VAG-2195) and NCT00431132 (VAG 1748).
Level of evidence: II.