A dose-escalating pilot study of sterically stabilized, pegylated liposomal doxorubicin (Lipo-Dox) in patients with metastatic breast cancer

Doxorubicin is considered among the most active single agents used against advanced breast cancer. Recent advances in the design of liposomes as carriers of cytotoxic drugs have resulted in a new formulation of doxorubicin with improved pharmacokinetic and tumor-localizing properties. The objectives of this dose-escalating pilot study were to evaluate the efficacy and safety of the sterically stabilized, pegylated liposomal doxorubicin (Lipo-Dox) for the treatment of metastatic breast cancer. Lipo-Dox was given at the dosage of 45 mg/m² over 1 hr of intravenous infusion every 4 weeks initially and could be escalated up to a maximum of 60 mg/m². Response was assessable in 17 of 19 intent-to-treat patients. An objective response was achieved in 41.2% (95% confidence interval: 17.8%-64.6%) of patients (5.9% complete response and 35.3% partial response), and 23.5% had stable disease. Median time to disease progression was 163 days. Major treatment-related toxicities included neutropenia, stomatitis, and skin toxicity in this dose-escalation program. Impressively, no grade 4 toxicities have ever been observed. The only grade 3 nonhematological toxicity ever to occur was reversible skin toxicity, presented as palmar-plantar erythrodysthesia. No severe nausea/vomiting, wig-necessary alopecia, or significant cardiac function change were encountered. In conclusion, Lipo-Dox is shown by this first reported pilot study to be an active agent for treatment of advanced breast cancer with a safety profile that differs markedly from free doxorubicin. The dosage of 45-60 mg/m² every 4 weeks was well tolerated. Because myelosuppression and other nonhematological toxicities associated with Lipo-Dox were generally mild and acceptable, further assessment of this drug particularly in combination with other chemotherapeutic drugs in the management of early or advanced breast cancer is suggested.