REGRESSION OF UTERINE LEIOMYOMATA TO THE ANTIPROGESTERONE RU486 - DOSE-RESPONSE EFFECT

Objective: To study the response of uterine leiomyomata to three daily doses of RU486 (5, 25, and 50 mg). Design: Prospective nonrandomized trial of women with symptomatic leiomyomata.Setting: Patients from the clinical practice of the authors at the University of California, San Diego Medical Center. Patients: Ten patients with symptomatic leiomyo mata previously reported after treatment with 50 mg of RU486 daily for 3 months. Eleven patients treated with 25 mg of RU486 daily and nine patients placed on 5 mg of RU486 daily for 12 weeks. Main Outcome Meas ures: Changes in leiomyomata volume as measured with vaginal ultrasoun ds at baseline and monthly thereafter. Frequent blood samples for hema tology, chemistry, and hormone levels were obtained. Twenty-four-hour urine collections for free cortisol and creatinine were obtained at ba seline and at 12 weeks. Results: All three doses induce ovarian acycli city. Administration of 50 mg of RU486 decreases leiomyomata volume to 78.1% +/- 4.8% of baseline at 4 weeks, 60.5% +/- 6.6% at 8 weeks, and 51.0% +/- 9.2% after 12 weeks of treatment. Regressive response in pa tients treated with 25 mg of RU486 daily was 76.3% +/- 5.0% of baselin e at 4 weeks, 54.0% +/- 5.1% at 8 weeks, and 44.0% +/- 5.0% after 12 w eeks. At 5 mg of RU486, leiomyomata volume was 80.6% +/- 8.3% of basel ine after 4 weeks, 63.7% +/- 14.6% after 8 weeks, and 74.4% +/- 19.8% after 12 weeks of therapy. Conclusions: Although acyclicity is seen at all three doses, an effective dose to cause a clinically significant (50%) decrease in leiomyomata volume appears to be 25 mg daily.