DISEASE CHARACTERISTICS:

• Diagnosis of metastatic breast cancer
• Disease must have progressed despite prior systemic hormonal therapy
• Measurable disease
• No brain metastases unless stable for 1 month or more after radiation therapy
• Hormone receptor-positive disease

PATIENT CHARACTERISTICS:

• Female
• Pre- or post-menopausal
• Karnofsky performance status 80-100%
• Absolute neutrophil count ≥ 1,500/mm³
• Platelet count > 100,000/mm³
• Hemoglobin > 9 g/dL
• Bilirubin < 2 times upper limit of normal (ULN)
• AST and ALT < 2 times ULN (≤ 5 times ULN if liver has tumor involvement)
• Creatinine < 2 times ULN
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during study and for 3 months after completion of study treatment
• No pain uncontrolled with the use of non-narcotic drugs (acetaminophen or nonsteroidal medications)
• No history of sensitivity to naltrexone
• No acute hepatitis or liver failure
• No positive urine screen for opiods

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• Recovered from prior therapy
• No hormonal therapy within the past 2 weeks
• No chemotherapy, immunotherapy, or biologic therapy within the past 3 weeks
• No short-acting or long-acting opioid medication (including morphine, meperidine, oxycodone, hydromorphone, hydrocodone, fentanyl, or tramadol) within the past 10 days
• No concurrent immunosuppressive therapy for patients with autoimmune diseases, organ transplant, or other indications
• No concurrent surgery or other procedures that will require narcotic analgesics
• No concurrent narcotic analgesics for pain
• No concurrent short-acting or long-acting opioid medication (including morphine, meperidine, oxycodone, hydromorphone, hydrocodone, fentanyl, or tramadol)