Purpose: Anthracyclines are a component of breast cancer chemotherapy regimens in both adjuvant and metastatic settings. Anthracycline rechallenge for metastatic disease, for those previously exposed to adjuvant anthracyclines, may not be considered because of concerns about efficacy, tolerability, and cumulative cardiotoxicity.

Patients and Methods: This prospective, multicenter, single-arm, phase II trial examined the efficacy and safety of pegylated liposomal doxorubicin (PLD) 35 mg/m² plus cyclophosphamide 600 mg/m² as first-line therapy, delivered every 3 weeks, in 70 patients who developed metastatic disease more than 12 months after completion of an adjuvant anthracycline-containing regimen. Seven patients discontinued treatment early and were excluded from the efficacy analysis.

Results: After a median of six cycles, the objective response rate was 38%. An additional 33% of patients achieved stable disease lasting more than 6 months, for an overall clinical benefit rate of 71%. The estimated median time to progression was 12.2 months. Median overall survival time was 16.5 months. Clinical response was equally robust in patients with and without prior taxane exposure. Treatment was well tolerated. The most common grade 3 to 4 toxicities were palmar-plantar erythrodysesthesia (PPE; 10%), dyspnea (9%), and neutropenia (9%). One (1.4%) of 70 patients discontinued treatment as a result of PPE. One patient (1.4%) experienced an infusion reaction requiring discontinuation. No symptomatic cardiac events were observed.

Conclusion: PLD plus cyclophosphamide is effective and well tolerated in patients with metastatic breast cancer who have received prior adjuvant anthracycline-containing chemotherapy. The majority of patients experienced a clinical benefit without any significant impact on cardiac function.