Twelve-month safety and efficacy of low-dose mifepristone for uterine myomas

Abstract

Study objectives: The primary aim was to assess long-term effects of low-dose mifepristone on myoma regression, symptoms, and endometrial pathology. The secondary aim was to assess regrowth of myomas after cessation of mifepristone.

Design: Prospective, open-label, randomized, controlled trial of 5 mg versus 10 mg mifepristone daily for 1 year, in women with large, symptomatic myomas, with variable follow-up among a subset of subjects (Canadian Task Force classification II-2).

Setting: University research group set in a community hospital.

Patients: Forty premenopausal women with large, symptomatic myomas.

Intervention: Oral mifepristone 5 or 10 mg daily for 1 year.

Measurements and main results: Mean uterine volumes decreased in both groups by 48% after 6 months of mifepristone and by 52% to 53 % in both groups after 12 months. Amenorrhea occurred in 61% to 65% at 6 months, and 40% to 70 % at 12 months. Eighty endometrial biopsies were performed. Simple hyperplasia was seen in 5 (13.9 %) of 36 subjects at 6 months and 1 (4.8 %) of 21 at 12 months. All cases of hyperplasia occurred in the 10 mg group. No endometrial sample showed cytologic atypia. Nine women were followed posttreatment for an average of 5.7 months. Uterine volumes increased among most of these subjects, although they remained on average 42% less than baseline.

Conclusions: Long-term administration of low-dose mifepristone results in myoma shrinkage and amelioration of symptoms; modest rates of low-grade endometrial hyperplasia, but no evidence of premalignant potential, also occur. Regrowth occurs slowly following cessation of the drug.