Inclusion Criteria

DISEASE CHARACTERISTICS:

- Unequivocal diagnosis of metastatic breast cancer

- Bidimensionally measurable disease

- No uncontrolled CNS metastases

- No disease that is evaluable only, including blastic bone disease, malignant ascites,
and malignant pleural effusion

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Menopausal status:

- Not specified

Performance status:

- SWOG 0-2 OR

- Karnofsky 60-100%

Life expectancy:

- At least 18 weeks

Hematopoietic:

- Platelet count at least 50,000/mm^3

- PT and PTT within normal limits

- Neutrophil count at least 2,000/mm^3

Hepatic:

- Bilirubin no greater than 1.2 mg/dL

- Transaminases no greater than 3 times normal

Renal:

- Creatinine no greater than 1.6 mg/dL OR

- Creatinine clearance at least 70 mL/min

Other:

- No active infections requiring antibiotics

- No viral hepatitis allowed

- Seronegative for hepatitis B or C

- Not pregnant or nursing

- Fertile patients must use effective contraception during and for 2 months following
study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No concurrent immunotherapy

Chemotherapy:

- 2 prior chemotherapy regimens for metastatic disease allowed as adjuvant therapy or
for advanced disease (may include high dose chemotherapy with stem cell support)

- At least 4 weeks since prior chemotherapy

- At least 6 weeks since prior nitrosourea or mitomycin therapy

- No other concurrent chemotherapy

Endocrine therapy:

- 2 prior hormonal therapy regimens for metastatic disease as adjuvant therapy or for
advanced diseases allowed

- At least 2 weeks since prior hormonal therapy (at least 4 weeks in case of disease
progression while receiving hormonal therapy after initial response)

- No concurrent hormonal therapy except oral contraceptives

- No concurrent use of steroids except for management of severe or life- threatening
toxic effects arising from bryostatin 1

Radiotherapy:

- At least 2 weeks since prior radiotherapy

- No concurrent radiotherapy

Surgery:

- Not specified

Other:

- No concurrent use of drugs known to interfere with platelet function, such as aspirin
or NSAIDs (including ibuprofen)

- No concurrent use of anticoagulants

- At least 2 weeks since prior use of aspirin

- At least 2 days since prior use of NSAIDS

- Concurrent use of acetaminophen to control pain is allowed

- If acetaminophen inadequate for pain control, concurrent use of oral narcotics such
as codeine or oxycodone is allowed