PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy for gastric or gastroesophageal junction cancer No prior irinotecan (CPT-11) or other camptothecin Endocrine therapy: Not specified Radiotherapy: No prior abdominal or pelvic radiotherapy No prior radiotherapy to greater than 25% of bone marrow No prior radiotherapy to measurable or evaluable indicator lesions At least 4 weeks since major radiotherapy (chest radiotherapy) Surgery: At least 3 weeks since major surgery and recovered At least 2 weeks since minor surgery and recovered Other: No other concurrent investigational agents