As many as three fourths of premenopausal women may have uterine leiomyomata (fibroids). Surgical removal of fibroids accounts for about one third of all hysterectomies in the United States (i.e., about 170,000 procedures). Because leiomyomata contain progesterone receptors, the competitive progesterone receptor-binder mifepristone could cause leiomyomata to shrink. Eisinger and colleagues studied two dosages of mifepristone in the treatment of leiomyomata.

They recruited 40 healthy, premenopausal women who met criteria for surgical removal of uterine leiomyomata, who had uterine volumes of at least 300 mL on ultrasonography, and who agreed to use nonhormonal contraception. Women who were trying to become pregnant were excluded, as were women with gynecologic, medical, or significant psychologic symptoms, and women with elevated levels of follicle-stimulating hormone (FSH), indicating declining ovarian function. After baseline screening, participants were randomly assigned to treatment with 5 or 10 mg of mifepristone daily for six months. Uterine volume was assessed every two months by ultrasonography, and blood levels of hemoglobin, liver enzymes, and FSH were monitored. Endometrial biopsy was performed on all participants after six months. The women maintained logs of symptoms and menstrual flow, using scoring scales to quantify symptom severity and degree of blood loss.

The treatment groups were similar in age, educational status, obstetric history, uterine volume, body mass index, and levels of hemoglobin and FSH. Two women treated with 5 mg of mifepristone did not complete the study. Mean uterine volume decreased significantly in both groups, although there was no significant difference between the groups. After two months, 17 of the 20 women (85 percent) taking 5 mg of mifepristone were amenorrheic, but by the end of six months, only 11 of the 18 women still enrolled in the study (61 percent) were amenorrheic. In the group treated with 10 mg of mifepristone, 85 percent were amenorrheic after three months, and 65 percent were amenorrheic by six months.

In both groups, women reported significant declines in pelvic pressure symptoms. Women in both groups reported an increase in hot flushes. The increase was significant in women taking 10 mg of mifepristone, where the number rose from one (5 percent) to 11 (55 percent). In the 5-mg treatment group, the number of women reporting hot flushes rose from seven (35 percent) to nine (45 percent). The prevalence of headache, mood swings, nausea, and fatigue decreased in both groups. Endometrial samples were obtained from 36 patients during the study. No atypical hyperplasia was found, but simple endometrial hyperplasia was detected in 28 percent of the women, with no significant difference between treatment groups.

The authors conclude that mifepristone therapy results in regression of leiomyomata with improvement in symptoms. This therapy may provide an alternative to hysterectomy or myomectomy, particularly in younger women who wish to retain fertility. The therapy also may let perimenopausal women manage symptoms until menopause, when fibroids regress. In addition, mifepristone may provide preoperative reduction of lesions comparable to that of the GnRH analogs at lower cost and with fewer side effects and greater patient acceptability.