Lack of activity of stealth liposomal doxorubicin in the treatment of patients with anthracycline-resistant breast cancer

Purpose: We conducted a single-institution phase II clinical trial to determine the objective response rate, duration of response, time to progression, and overall survival in patients with anthracycline-resistant breast cancer treated with Doxil. Patients and methods: Patients with metastatic breast cancer were eligible if they had disease progression while receiving an anthracyclinecontaining regimen or developed evidence of metastatic disease during or within 6 months after the last cycle of an anthracycline-containing adjuvant regimen. Prior treatment with liposomal doxorubicin was not allowed. Patients received a dose of 50 mg/m² infused every 4 weeks via a peripheral vein or central line. Doxil was administered for a total of six cycles or until disease progression. Results: We treated 11 patients with stage IV breast cancer of whom two had never received chemotherapy for their metastatic disease. Most had a performance status of 1 and had visceral involvement as their dominant site of disease. All patients had received prior therapy with doxorubicin. No clinical evidence of congestive heart failure or cardiac toxicity was observed. The most common toxicities were nonhematologic and were mostly grade 1/2. These included fatigue, nausea, vomiting, and stomatitis. Significant myelosuppression was only observed in one patient. No complete or partial response was observed. There were two patients who had a minimal response and two other patients who had evidence of stable disease. Conclusion: Doxil was well tolerated with minimal toxicity. However, the lack of antitumor activity in anthracycline-resistant breast cancer patients indicates that further evaluation in this patient population is not warranted.