the present invention relates to the use of fosfestrol in a method of curative or palliative treatment of prostate cancer in male mammals , said method comprising orally administering fosfestrol in a daily dosage of at least 1 , 000 mg . the inventors have discovered that fosfestrol when administered in very high oral dosages is effective in the treatment of prostate cancer , especially hormone resistant prostate cancer , without giving rise to serious side effects , such as thromboembolic toxicity or mortality . the invention further provides an oral dosage unit comprising at least 500 mg , of fosfestrol .