Purpose: Progestins have definite activity against advanced or recurrent endometrial carcinoma. Both parenteral and oral progestins yield similar serum levels and response rates, which range from 18% to 34%. The one major study that used oral medroxyprogesterone acetate (MPA) noted a response rate at the lower end of the range (18%) and much poorer progression-free and overall survival times (4 and 10.5 months, respectively) than previously reported. The present study sought to confirm this earlier study of oral MPA, to assess the importance of prognostic factors such as histologic grade and receptor levels, and to determine whether a higher dose of MPA would yield a higher response rate.
Patients and methods: Two hundred ninety-nine eligible women with advanced or recurrent endometrial carcinoma were randomized to receive oral MPA either 200 mg/d or 1, 000 mg/d until unacceptable toxicity intervened or their disease progressed.
Results: Among 145 patients receiving the low-dose regimen, there were 25 complete (17%) and 11 partial (8%) responses for an overall response rate of 25%. The 154 patients receiving the high-dose regimen experienced 14 (9%) complete and 10 (6%) partial responses for an overall response rate of 15%. Median durations of progression-free survival were 3.2 months and 2.5 months for the low-dose and high-dose regimens, respectively. Median survival durations were 11.1 months and 7.0 months, respectively. The adjusted relative odds of responding to the high-dose regimen compared with the low-dose regimen was 0.61 (90% confidence interval, 0.36 to 1.04). Prognostic factors having a significant impact on the probability of response included initial performance status, age, histologic grade, and progesterone receptor concentration. Compliance with oral therapy was documented with serum levels 1 month after starting therapy, when possible. MPA levels were commensurate with the assigned dose and schedule.
Conclusion: Oral MPA is active against endometrial carcinoma. Response to progestin therapy is more frequent among patients with a well-differentiated histology and positive progesterone receptor status. This study provides no evidence to support the use of MPA 1,000 mg/d orally instead of MPA 200 mg/d orally. In fact, the trends suggest the opposite. The use of oral MPA 200 mg/d is a reasonable initial approach to the treatment of advanced or recurrent endometrial carcinoma, particularly those lesions that are well-differentiated and/or progesterone receptor-positive (> 50 fmol/mg cytosol protein). Patients with poorly differentiated and/or progesterone receptor levels less than 50 fmol/mg cytosol protein had only an 8% to 9% response rate.