Evaluation of the mechanism of action of a progestin on endometrial andenocarcinoma.

7 patients 5 with persistent or recurrent adenocarcinoma of the endometrium and 2 with in situ carcinoma were treated with medroxyprogesterone acetate (Depo-Provera) 2000 mg given initially followed by 1000 mg weekly given im. Toxicity was not observed. 3 of the 5 patients with invasive carcinoma had apparent complete remission. In the 2 with in situ carcinoma serial biopsies showed disappearance of neoplasms. 3 reasons are given for the possible mechanism of action of this drug in the treatment of endometrial adenocarcinoma: 1) the immunosuppressive properties of medroxyprogesterone 2) alteration of the estrogen support to an endometrial carcinoma by massive progestin therapy and 3) a direct effect on the tumor cells.