PS-341 in Treating Women With Metastatic Breast Cancer

DISEASE CHARACTERISTICS:

* Histologically confirmed adenocarcinoma of the breast

  * Metastatic disease
* At least 1 unidimensionally measurable lesion

  * At least 20 mm by conventional techniques OR
  * At least 10 mm by spiral CT scan
* Previously treated with 1 prior chemotherapy regimen (with or without trastuzumab \[Herceptin\]) for metastatic disease

  * Relapse during or within 6 months after completion of adjuvant chemotherapy considered treatment failure
* No known brain metastases
* Hormone receptor status:

  * Not specified

PATIENT CHARACTERISTICS:

Age:

* 18 and over

Sex:

* Female

Menopausal status:

* Not specified

Performance status:

* ECOG 0-2

Life expectancy:

* More than 3 months

Hematopoietic:

* WBC at least 3,000/mm\^3
* Absolute neutrophil count greater than 1,500/mm\^3
* Platelet count at least 100,000/mm\^3

Hepatic:

* Bilirubin normal
* SGOT/SGPT no greater than 2.5 times upper limit of normal

Renal:

* Creatinine normal OR
* Creatinine clearance at least 60 mL/min

Cardiovascular:

* No symptomatic congestive heart failure
* No unstable angina pectoris
* No cardiac arrhythmia

Other:

* No uncontrolled concurrent illness
* No ongoing or active infection
* No psychiatric illness or social situation that would preclude study
* No prior allergic reaction attributed to compounds of similar chemical or biological composition to bortezomib
* No other prior malignancy within the past 5 years unless curatively treated and disease free
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

* See Disease Characteristics

Chemotherapy:

* See Disease Characteristics
* At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin) and recovered

Endocrine therapy:

* Prior hormonal therapy for metastatic disease allowed
* At least 4 weeks since prior hormonal therapy and recovered

Radiotherapy:

* At least 4 weeks since prior radiotherapy and recovered

Surgery:

* Not specified

Other:

* Prior adjuvant therapy allowed
* At least 4 weeks since prior investigational drugs and recovered
* No other concurrent investigational or commercial agents or therapies for breast cancer
* No concurrent combination antiretroviral therapy for HIV