Activity of exemestane in metastatic breast cancer after failure of nonsteroidal aromatase inhibitors: A phase II trial

Purpose: To evaluate the antitumor activity and toxicity of a new steroidal aromatase inactivator, exemestane, in postmenopausal women with metastatic breast cancer who had progressive disease (PD) after treatment with a nons teroidal aromatase inhibitor, Patients and Methods: In this phase II trial, eligible patients were treate d with exemestane 25 mg daily (n = 241) followed, at the time PD was determ ined, by exemestane 100 mg daily (n = 58). Results: On the basis of the intent-to-treat analysis by independent review , exemestane 25 mg produced objective responses in 6.6% of patients (95% co nfidence interval [CI], 3.8% to 10.6%) and overall success (complete respon se + partial response + no change for 24 weeks or longer) in 24.3% (95% CI, 19.0% to 30.2%). The median durations of objective response and overall su ccess were 58.4 weeks (95% CI, 49.7 to 71.1 weeks) and 37.0 weeks (95% CI, 35.0 to 39.4 weeks), respectively. Increasing the dose of exemestane to 100 mg upon the development of PD produced one partial response (1.7%; 95% CI, 0.0% to 9.2%). Both dosages were well tolerated and were discontinued beca use of adverse events in only 1.7% of patients. Conclusion: Exemestane 25 mg once daily seems to be an attractive alternati ve to chemotherapy for the treatment of patients with metastatic breast can cer after multiple hormonal therapies have failed. J Clin Oncol 18:2234-224 4. (C) 2000 by American Society of Clinical Oncology.