Randomized trial of medroxyprogesterone acetate for the prevention of endometrial pathology from adjuvant tamoxifen for breast cancer: SWOG S9630

Ronald K. Potkul, Joseph M. Unger, Robert B Livingston, Katherine D. Crew, Sharon P. Wilczynski, Caryl G. Salomon, Barbara L. Smith, Lucas Wong, David L. Campbell, David E. Einspahr, Garnet L. Anderson, Dawn Hershman, Gary E. Goodman, Powel H. Brown, Frank L. Meyskens, Kathy S. Albain

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The proliferative effect of adjuvant tamoxifen on the endometrium can potentially result in endometrial abnormalities, including cancer in postmenopausal women. We conducted a randomized, controlled trial to assess endometrial pathological diagnoses in postmenopausal women with early stage, ER-positive breast cancer without endometrial pathology at baseline. They were assigned to tamoxifen alone versus tamoxifen plus cyclical medroxyprogesterone acetate (MPA 10 mg for 14 days every 3 months) for 5 years. Endovaginal sonograms (EVS) +/- endometrial biopsies (EMB) were required at baseline, 2 and 5 years. Of 313 patients registered, 296 were eligible and 169 (57%; 89, tamoxifen; 80, tamoxifen+MPA) were evaluable (completed year-2 EVS, with an EMB if stripe width was ?5 mm). Sixty (67%) of these in the tamoxifen arm had an endometrial stripe width ? 5 mm (and underwent subsequent EMB) compared with 48 (60%) in the tamoxifen+MPA arm (P = 0.40). There were four cases of proliferative endometrium and one simple hyperplasia on the tamoxifen arm (6% (95% confidence interval (CI): 2-13%) among evaluable patients and one proliferative endometrium on the tamoxifen+MPA arm (P = 0.11). The overall fraction with benign endometrial abnormalities at year 2 was 3.6% (6/169; 95% CI: 1.3-7.6%), with only 1 (of 102) new benign proliferative event at year 5. The event rate in both arms was much lower than projected, making treatment arm comparisons less informative. A normal endometrium prior to tamoxifen may provide reassurance regarding future endometrial events. However, validation in a larger trial is needed before changing practice in asymptomatic, postmenopausal women.

Original languageEnglish (US)
Article number16024
Journalnpj Breast Cancer
Issue number1
Publication statusPublished - Dec 14 2016


ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Pharmacology (medical)

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