RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die.

PURPOSE: Phase II trial to study the effectiveness of bryostatin 1 in treating patients with stage IV breast cancer.

OBJECTIVES:

• Determine the clinical response of patients with stage IV breast cancer to bryostatin 1.
• Determine the efficacy of this regimen in these patients.
• Estimate the pharmacokinetic parameters of bryostatin 1 when given as 24 hour infusion.
• Determine the ability of this regimen to regulate lymphocyte function in these patients.
• Determine the effect of this regimen on platelet function and protein kinase C activity in these patients.

OUTLINE: Patients receive bryostatin 1 IV over 24 hours. Treatment continues weekly in the absence of disease progression or unacceptable toxicity.

Patients are followed every 4-8 weeks for tumor response.

PROJECTED ACCRUAL: A total of 14-25 patients will be accrued for this study.

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