OBJECTIVES: Primary * Determine the time to progression in women with metastatic breast cancer who have progressed after prior chemotherapy and are now treated with amonafide. * Determine the overall response rate (complete and partial response) in patients treated with this drug. * Determine the safety of a phenotypically driven dosing regimen of this drug in these patients. Secondary * Determine the time to tumor response, duration of response, and time to treatment failure in patients treated with this drug. * Determine the overall survival of patients treated with this drug. * Determine the pharmacokinetic profile of this drug in these patients. OUTLINE: This is an open-label, multicenter study. Patients receive amonafide IV over 1 hour on days 1-5. Treatment repeats every 21 days for at least 5 courses in the absence of disease progression or unacceptable toxicity. Patients with stable or responding disease may receive additional courses (beyond 5 courses) at the investigator's discretion. Patients are followed at 30 days and then every 3 months. PROJECTED ACCRUAL: A total of 175 patients will be accrued for this study within 1 year.
DISEASE CHARACTERISTICS: * Histologically confirmed breast cancer * Metastatic (stage IV) disease * Relapsed after 1 of the following prior therapy regimens\*: * Adjuvant therapy containing an anthracycline and a taxane * Adjuvant anthracycline therapy followed by first-line metastatic treatment containing a taxane NOTE: \*No relapse within 12 months of initiation of prior therapy * Measurable disease by CT scan or MRI * No ascites, pleural effusions, or osteoblastic bone metastases as the only site of measurable disease * Refractory to hormonal anticancer therapy completed more than 4 weeks before study therapy * HER2/neu positive allowed provided patient received prior trastuzumab (Herceptin®) * MUGA or echocardiogram normal while on trastuzumab * No known history of or current brain or leptomeningeal metastases * Hormone receptor status: * Not specified PATIENT CHARACTERISTICS: Age * Over 18 Sex * Female Menopausal status * Not specified Performance status * ECOG 0-2 Life expectancy * At least 12 weeks Hematopoietic * WBC at least 3,000/mm\^3 * Neutrophil count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 * Hemoglobin at least 10.0 g/dL * No clinically significant abnormal hematological parameters Hepatic * Bilirubin no greater than 1.5 times upper limit of normal (ULN) * Alkaline phosphatase no greater than 2.5 times ULN (5 times ULN in case of liver metastases) * AST or ALT no greater than 2.5 times ULN (5 times ULN in case of liver metastases) Renal * Creatinine no greater than 1.5 times ULN Cardiovascular * See Disease Characteristics * No myocardial infarction within the past 3 months * No unstable angina pectoris * No New York Heart Association class III or IV heart disease * No uncontrolled arrhythmia * No cardiac insufficiency * No uncontrolled hypertension * LVEF at least 50% OR at least lower limit of normal Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception 4 weeks before, during, and for at least 4 weeks after study participation * No preexisting neuropathy (motor or sensory) greater than grade 2 * No clinically significant abnormal biochemical parameters * No clinically significant active infection * No other prior malignancy except cured nonmelanoma skin cancer or curatively treated carcinoma in situ of the cervix * No other serious illness or medical condition * No psychological illness or condition that would preclude study participation * No other known condition that would preclude study participation PRIOR CONCURRENT THERAPY: Biologic therapy * See Disease Characteristics * More than 3 months since prior trastuzumab * More than 2 weeks since prior growth factor therapy (i.e., filgrastim \[G-CSF\] or sargramostim \[GM-CSF\]) * No concurrent systemic anticancer immune modulators Chemotherapy * See Disease Characteristics Endocrine therapy * See Disease Characteristics * More than 4 weeks since prior hormonal therapy * No concurrent anticancer hormonal therapy * No concurrent chronic systemic steroids * Concurrent topical or inhaled steroids for dermatological or allergy/asthma conditions allowed provided therapy was initiated prior to study enrollment * Concurrent hormone replacement therapy allowed provided therapy was initiated prior to study enrollment Radiotherapy * More than 30 days since prior radiotherapy * No concurrent radiotherapy directed at target lesions Surgery * At least 4 weeks since prior major surgery and recovered Other * More than 30 days since prior investigational new drug * More than 2 weeks since prior blood transfusion * No other concurrent systemic anticancer agents, including immunosuppressive agents * No other concurrent investigational agents * Concurrent bisphosphonates allowed provided therapy was initiated prior to study enrollment