Estramustine potentiates taxane in prostate and refractory breast cancers.

Estramustine is nornitrogen mustard linked to estradiol. It binds to tubulin and to microtubule-associated proteins, depolymerizes cytoplasmic microtubules, and disrupts the nuclear matrix. It has limited clinical activity as a single agent, but preclinical studies suggest that it is an effective modulator of antitubulins. This paper reviews the rationale for the combination of estramustine with antitubulins and the clinical toxicity profile of estramustine. Also discussed are data from phase II studies in hormone-resistant prostate cancer and in taxane-resistant breast cancer that suggest that the modulation of antitubulins by estramustine that has been demonstrated in vitro is indeed clinically relevant. Finally, current approaches to improving the tolerability of estramustine are described.