Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically proven metastatic breast cancer

- HER2/neu-positive (overexpressing) tumor tissue

- Failed prior trastuzumab (Herceptin) therapy with or without chemotherapy

- Resected stage IV disease allowed if evidence of disease

- Bidimensionally measurable or evaluable disease

- No lesions in previously irradiated field except nonbone lesions progressive
after radiotherapy

- No pleural effusions

- No blastic or mixed bony metastases

- No palpable abdominal masses

- No leptomeningeal disease

- Brain metastases allowed if:

- No concurrent use of steroids

- At least 3 months since prior brain irradiation

- No evidence of progression of metastases

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Sex:

- Female

Menopausal status:

- Not specified

Performance status:

- Karnofsky 70-100%

Life expectancy:

- At least 3 months

Hematopoietic:

- Granulocyte count at least 1,500/mm^3

- Hemoglobin at least 8.0 g/dL

- Platelet count at least 100,000/mm^3

Hepatic:

- AST/ALT no greater than 2 times upper limit of normal (ULN)

- Bilirubin no greater than 1.5 times ULN

Renal:

- Creatinine no greater than 1.5 mg/dL

Cardiovascular:

- LVEF at least 50%

Other:

- Not pregnant

- Negative pregnancy test

- Fertile patients must use effective barrier contraception

- No other prior malignancy within the past 5 years except adequately treated carcinoma
in situ of the cervix or nonmelanoma skin cancer

- No other serious medical illness

- No severe infection

- No severe malnutrition

- No prior allergic reactions to sulfonamides or celecoxib

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- See Disease Characteristics

- Prior trastuzumab (Herceptin) for breast cancer allowed, either as
adjuvant/neoadjuvant or for metastatic disease

Chemotherapy:

- See Disease Characteristics

- At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin) and
recovered

- Prior cytotoxic therapy for breast cancer allowed, either as adjuvant/neoadjuvant or
for metastatic disease

Endocrine therapy:

- See Disease Characteristics

- At least 3 weeks since prior hormonal therapy

- Prior exogenous hormonal therapy for stage IV disease and/or as adjuvant therapy
allowed

Radiotherapy:

- See Disease Characteristics

- At least 4 weeks since prior radiotherapy and recovered

- Prior localized radiotherapy allowed if no influence on the signal measurable lesion

- Concurrent localized radiotherapy allowed if no influence on the signal measurable
lesion

Surgery:

- See Disease Characteristics

- At least 3 weeks since prior major surgery and recovered

- At least 2 weeks since prior minor surgery and recovered