Alternating tamoxifen and medroxyprogesterone acetate in postmenopausal advanced breast cancer patients--short and long term endocrine effects.

The endocrine effects of alternating tamoxifen and medroxyprogesterone acetate have been evaluated in 26 post-menopausal patients with metastatic breast cancer. Endocrine evaluations included the RIA determination of plasma levels of sex-hormone binding globulin, follicle-stimulating hormone, luteinizing hormone, estradiol, prolactin, cortisol, and testosterone. The evaluation of the study parameters at different intervals during therapy indicates that with this schedule an alternate sequential effect on the endocrine system is achievable because each drug exerts its own endocrine activity that is completely reversed when the other drug is administered. We can hypothesize that the same alternate activity as seen on the endocrine system could be obtained also on other tissues and organs including tumors.