The objective of this study is to assess the efficacy and toxicity of a 2 weekly regimen containing irinotecan combined with leucovorin-modified 5-fluorouracil in the setting of relapsed or refractory upper gastrointestinal tumours. Patients with locally advanced or metastatic adenocarcinoma originating from the oesophagogastric junction, stomach or pancreas who have previously received chemotherapy and have either failed to respond or who have relapsed after an initial response will be eligible for treatment in this study.