SAN FRANCISCO – Long-term mifepristone therapy for Cushing’s syndrome was associated with endometrial thickening, with some women showing histologic changes consistent with progesterone receptor modulator–associated endometrial changes, in two studies of a total of 35 patients.

The women received 300-1,200 mg/day of mifepristone in the 24-week open-label Study of the Efficacy and Safety of Mifepristone in the Treatment of Endogenous Cushing’s Syndrome (SEISMIC) and in an extension of the study in 18 patients who continued for a median of 27 months (range, 14-43 months).

The women received 300-1,200
mg/day of mifepristone (Korlym) in the 24-
week open-label Study of the Effica
cy and Safety of Mifepristone in the
Treatment of Endogenous Cushing’s
Syndrome ( SEISMIC) and in an ex
tension of the study in 18 patients
who continued for a median of 27
months (range, 14-43 months). Korlym is indicated to control hyperglycemia secondary to hypercortisolism in adults with endogenous Cushing's syndrome who have type 2 diabetes mellitus or glucose intolerance and have failed surgery or are not candidates for surgery, according to the product's labeling information.*

Transvaginal ultrasounds in 26 women at baseline and 27 women after the start of the study showed that mifepristone use was associated with endometrial thickening, especially in premenopausal women. The endometrium thickened by more than 5 mm in 8 of 26 premenopausal women (31%) and in two of nine postmenopausal women (22%), with thickening of more than 10 mm in 4 premenopausal women (15%) and one postmenopausal woman (11%), Dr. Ty Carroll reported.

Four (22%) of the 18 women in the extension study who’d been on mifepristone for 14 or more weeks and who had endometrial thickening greater than 20 mm developed clinically relevant endometrial bleeding and underwent hysterectomy (three patients) or dilation and curettage. The endometrial thickening ranged from 25 to 55 mm in these women, who remained on mifepristone therapy throughout the studies, Dr. Carroll and his associates reported in a featured poster presentation at the annual meeting of the Endocrine Society.

"Gynecologic consultation may be required in patients with persistent endometrial bleeding," said Dr. Carroll of the Medical College of Wisconsin, Milwaukee.

Vaginal bleeding of any kind occurred in 10 premenopausal women (38.5%) and two postmenopausal patients (7%). Three premenopausal women reported minor bleeding upon starting mifepristone, and one premenopausal woman reported minor bleeding after stopping mifepristone. Two premenopausal and two postmenopausal women reported intermittent, self-limited spotting or bleeding during treatment.

Bleeding did not always occur following endometrial thickening. Three patients with endometrial thickening greater than 20 mm after 6 months reported no bleeding.

Mifepristone use was not associated with precancerous endometrial lesions. In 33 endometrial biopsies obtained from 15 patients (11 premenopausal and 4 postmenopausal women), 31 biopsies (94%) had benign histology with variable findings of inactive, atrophic, disordered, or mixed-pattern endometrium, and 18 biopsies (56%) showed findings of progesterone receptor modulator–associated endometrial changes. Simple hyperplasia in one patient could not be confirmed on a repeat biopsy, and complex atypical endometrial hyperplasia in a second patient was thought to have existed prior to the study, Dr. Carroll reported. No patients showed evidence of endometrial carcinoma.

Previous studies have reported progesterone receptor modulator–associated endometrial changes from the use of mifepristone, a competitive progesterone receptor antagonist, in doses of 5-200 mg/day that are not associated with glucocorticoid receptor antagonism.

In the current study, median endometrial thickness for the premenopausal women was 5 mm at baseline and 11 mm at 6 months, and for postmenopausal women, was 3 mm at baseline and 6.4 mm at 6 months. The gain was statistically significant for premenopausal but not postmenopausal women. Endometrial thickness continued to increase in the extension study.

The SEISMIC study included adult females with endogenous Cushing’s syndrome and type 2 diabetes or impaired glucose function and/or hypertension. It excluded premenopausal women with an endometrial thickness greater than 20 mm, postmenopausal women with an endometrial thickness greater than 5 mm, patients with ovarian cysts with diameters measuring greater than 5 cm (premenopausal) or 2 cm (postmenopausal), or women with free fluid pockets greater than 4 cm. Premenopausal participants had a mean age of 39 years, and postmenopausal participants had a mean age of 57 years.

Dr. Carroll has been a speaker and researcher for Corcept Therapeutics, which markets mifepristone. His coinvestigators were employees, contractors, or consultants for Corcept, which provided some funding for the study.

*Clarification, 8/22/2013: An earlier version of this story did not state that the brand of mifepristone used in this study was Korlym, which is indicated for treating Cushing's syndrome.

sboschert@frontlinemedcom.com

On Twitter @sherryboschert

Long-term mifepristone associated with endometrial thickening, bleeding