Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically confirmed metastatic adenocarcinoma of the breast
Prior treatment with an anthracycline (e.g., doxorubicin or epirubicin) and a taxane
(e.g., paclitaxel or docetaxel) either as adjuvant therapy or for advanced disease
Bidimensionally measurable disease Sentinel lesions must be outside of any prior radiation
port No resected disease or stage IV with no evaluable disease No brain metastases or
leptomeningeal disease No symptomatic lymphangitic pulmonary metastases Hormone receptor
status: Not specified

PATIENT CHARACTERISTICS: Age: 18 and over Sex: Female Menopausal status: Not specified
Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Hemoglobin
at least 9.0 g/dL Absolute neutrophil count at least 1,500/mm3 Platelet count at least
100,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL SGOT or SGPT no greater than 2
times upper limit of normal (ULN) (5 times ULN if liver metastases present) Renal:
Creatinine no greater than 2.0 mg/dL Cardiovascular: No active congestive heart failure No
uncontrolled angina No myocardial infarction within past 6 months Neurologic: No history
of an existing grade 3-4 peripheral neuropathy of any etiology Other: Not pregnant or
nursing Negative pregnancy test Fertile patients must use effective contraception No
allergy to camptothecin or its derivatives No concurrent serious infection No other
malignancy within the past 5 years except nonmelanoma skin cancer or carcinoma in situ of
the cervix No overt psychosis, mental disability, or incompetence No other life
threatening disease

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy No prophylactic
colony stimulating factors to prevent neutropenia (except when neutropenia fever occurs
despite dose reduction) Chemotherapy: See Disease Characteristics No greater than 3 prior
chemotherapy regimens for metastatic breast cancer or as either adjuvant or neoadjuvant
therapy At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas and mitomycin)
and recovered No other concurrent cytotoxic chemotherapy Endocrine therapy: Exogenous
hormonal therapy for stage IV disease and/or as adjuvant therapy allowed At least 3 weeks
since prior hormonal therapy except for: Patients who are highly unlikely to have a
withdrawal response to cessation of hormonal therapy (e.g., patients with disease that is
primarily resistant to hormonal therapy, patients without prior partial response, or
stabilization of disease lasting less than 6 months) Patients with new or extensive
visceral metastases Patients with rapidly progressive or symptomatic metastases during
hormonal therapy Radiotherapy: See Disease Characteristics At least 4 weeks since prior
radiotherapy and recovered No prior radiotherapy to greater than 50% of bone marrow No
concurrent radiotherapy Surgery: See Disease Characteristics At least 4 weeks since prior
major surgery and recovered No concurrent surgery Other: No other concurrent anticancer
treatment At least 28 days since other prior investigational drugs, including analgesics
or antiemetics No other investigational drugs during and for 28 days after the study No
drugs that induce or inhibit CYP3A enzyme