Bortezomib, Fluorouracil, and Leucovorin in Treating Patients With Metastatic or Unresectable Stomach Cancer

DISEASE CHARACTERISTICS: Diagnosis of gastric or gastroesophageal junction adenocarcinoma Metastatic or unresectable disease Progressive disease after receiving 1 prior chemotherapy regimen for metastatic disease comprising 1 of the following: Fluorouracil Cisplatin and irinotecan Capecitabine Taxanes Measurable disease No esophageal cancer No brain metastases PATIENT CHARACTERISTICS: Age Over 18 Performance status ECOG 0-2 OR Karnofsky 60-100% Life expectancy At least 3 months Hematopoietic Absolute neutrophil count ≥ 1,500/mm^3 Platelet count ≥ 100,000/mm^3 Hepatic Bilirubin normal AST and ALT ≤ 2.5 times upper limit of normal Renal Creatinine ≤ 1.5 mg/dL Cardiovascular No symptomatic congestive heart failure No unstable angina pectoris No cardiac arrhythmia No acute ischemia by EKG No significant conduction abnormality by EKG, including either of the following: Bifasicular block, defined as left anterior hemiblock in the presence of right bundle branch block Second or third degree atrioventricular block No history of cardiac or cerebrovascular disease due to hypotension and tachycardia Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception before, during, and for 6 months after study participation No ongoing or active infection No other uncontrolled illness No peripheral neuropathy ≥ grade 2 within the past 2 weeks No allergy to boron or mannitol PRIOR CONCURRENT THERAPY: Biologic therapy More than 4 weeks since prior immunotherapy Chemotherapy More than 4 weeks since prior chemotherapy (6 weeks for nitrosoureas) and recovered Endocrine therapy Not specified Radiotherapy More than 4 weeks since prior radiotherapy and recovered Surgery More than 2 weeks since prior major surgery Other No concurrent highly active anti-retroviral therapy for HIV-positive patients No other concurrent investigational agents