DISEASE CHARACTERISTICS: Histologically confirmed, locally advanced, metastatic or recurrent adenocarcinoma of the stomach or gastroesophageal junction Measurable disease CNS metastases allowed provided that patient has other sites of measurable disease, is neurologically stable, and is receiving no concurrent anticonvulsant therapy

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: CALGB 0-2 Life expectancy: Not specified Hematopoietic: WBC at least 3500/mm3 Absolute neutrophil count at least 1500/mm3 Platelet count at least 100,000/mm3 (no platelet transfusion within 7 days) Hemoglobin at least 9 g/dL Hepatic: Total bilirubin no greater than 1.5 mg/dL Transaminases no greater than 2.5 times upper limit of normal (ULN) (no greater than 5 times ULN if liver metastases) Renal: Creatinine no greater than 1.5 mg/dL OR Creatinine clearance at least 60 mL/min Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No concurrent uncontrolled medical or psychiatric condition No active uncontrolled infection No prior malignant disease within the past 5 years except curatively treated non-melanoma skin cancer and carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent prophylactic growth factors Chemotherapy: One prior adjuvant or neoadjuvant 5-FU-based chemotherapy regimen allowed At least 4 weeks since prior adjuvant or neoadjuvant chemotherapy (6 weeks if nitrosoureas or mitomycin) and recovered No prior therapy with a topoisomerase I inhibitor No other concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: One prior radiotherapy regimen allowed No prior radiation therapy to only site of measurable disease At least 4 weeks since prior radiation therapy and recovered No concurrent palliative radiation therapy Surgery: Not specified Other: See Disease Characteristics No other concurrent investigational antineoplastic therapy