Recent clinical studies have demonstrated a reduction of irinotecan (CPT-11) gastrointestinal toxicities when the CPT-11 is administered in combination with thalidomide in patients with diagnosis of gastric cancer. The main purpose of this study is to investigate the efficacy and safety of thalidomide and CPT-11 in advanced gastric cancer. The investigators will also manage to find out the possible interactions between CPT-11 pharmacokinetics and thalidomide to explain the previously described gastrointestinal toxicity reduction.