Failure of megestrol acetate to reverse tamoxifen induced endometrial neoplasia: two case reports

Tamoxifen's agonist effect on the endometrium has been associated with an i ncreased incidence of endometrial carcinoma. It has been suggested that thi s agonist effect may be averted by the concomitant use of a progestational agent. We report two patients with breast cancer receiving tamoxifen who de veloped endometrial carcinoma and atypical endometrial hyperplasia, respect ively. In one patient, this occurred despite the use of concomitant megestr ol acetate. In the other patient, tamoxifen-associated endometrial hyperpla sia persisted and progressed despite cessation of tamoxifen and initiation of megestrol acetate therapy. These cases may have implications for strateg ies to avert tamoxifen induced endometrial neoplasia.