[1] Univ La Laguna, Sch Med, Univ Hosp Canary Isl, Dept Gastroenterol, E-38320 Tenerife, Spain
[2] Natl Canc Ctr, Gastrointestinal Endoscopy Div, Tokyo 1040045, Japan
[3] Nuovo Regina Margherita Hosp, Dept Gastroenterol, I-00153 Rome, Italy
[4] Azienda Osped Univ San Giovanni Battista, SCDO Epidemiol Tumori, I-10126 Turin, Italy