Estramustine phosphate: a specific chemotherapeutic agent?

Estramustine phosphate is a nitrogen mustard derivative of estradiol that has been advocated for the treatment of prostatic cancer. The compound was designed with the hope that the estrogen moiety would direct the alkylating moiety to estrogen-dependent malignancies, where the alkylating moiety would be released specifically. Preclinical and clinical data are reviewed to determine to what extent that challenging concept is fulfilled. In addition, we have examined critically the efficacy of this drug for the treatment of prostatic cancer. From available data it appears that there is no evidence that the alkylating moiety of estramustine phosphate is specifically freed in estrogen-dependent tissues. Estramustine phosphate appears to be an active compound with acceptable toxicity in prostatic cancer. However, further clinical trials must be undertaken to clarify the future role of estramustine phosphate in the treatment of prostatic cancer.