RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Some patients may develop a resistance to chemotherapy drugs.

PURPOSE: Phase II trial to determine the reliability of a test for measuring drug resistance to paclitaxel in patients with metastatic breast cancer.

OBJECTIVES: I. Evaluate the proportion of patients with extreme, intermediate, and low drug resistance to paclitaxel using the Extreme Drug Resistance (EDR) Assay in patients with previously treated metastatic breast cancer. II. Assess response to paclitaxel therapy in patients who have undergone a pretreatment EDR assay. III. Assess time to tumor progression during paclitaxel therapy in patients who have undergone a pretreatment EDR assay. IV. Determine prospectively the predictive value of the EDR assay relative to clinical outcome by correlating assay results with clinical tumor response and time to tumor progression during paclitaxel therapy in these patients.

OUTLINE: This is an open label, single arm, blinded study. Patients' tumor tissue samples are collected by excisional biopsy, core biopsy, or malignant fluid aspiration, then tested by the Extreme Drug Resistance (EDR) Assay to determine probability of drug resistance to paclitaxel. After successful completion of the EDR assay (approximately 7 days), patients receive paclitaxel by intravenous infusion over 1-3 hours; treatment is repeated every 3 weeks. Treatment continues until there is documented evidence of tumor progression or unacceptable toxicity. Patients' clinical response to paclitaxel therapy is compared with the response predicted by the EDR assay.

PROJECTED ACCRUAL: 100 patients will be accrued to this study.

DISEASE CHARACTERISTICS: Metastatic breast cancer that is accessible for biopsy or aspiration Bidimensionally measurable disease with at least one diameter greater than 1 cm documented on x-ray or photograph, or a palpable lesion No brain metastases or carcinomatous meningitis Hormone receptor status: Not specified

PATIENT CHARACTERISTICS: Age: 18 and over Sex: Male or female Menopausal status: Not specified Performance status: SWOG 0-2 Life expectancy: Not specified Hematopoietic: Absolute neutrophil count greater than 1,500/mm3 Platelet count greater than 100,000/mm3 Hepatic: Bilirubin no greater than 2.0 mg/dL SGOT no greater than 3 times upper limit of normal (ULN) (no greater than 5 times ULN if metastatic to liver) Renal: Creatinine no greater than 2.0 mg/dL Calcium no greater than 12 mg/dL Cardiovascular: No myocardial infarction within 3 months prior to study No unstable angina or symptomatic congestive heart failure Other: No active or uncontrolled infection Not HIV positive No psychoses Not pregnant or nursing Effective contraception required of fertile women No second malignancy within past 5 years except: Adequately treated basal or squamous cell carcinoma of the skin In situ cancer of the cervix

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics Prior paclitaxel permitted if patient had disease-free interval of greater than 1 year Prior taxotere permitted Endocrine therapy: Not specified Radiotherapy: Not specified Surgery: Not specified