1. 1Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
2. 2Unit of Cancer Epidemiology, Centro di Riferimento Oncologico, National Cancer Institute IRCCS, Aviano, Italy.
3. 3Unit of Digestive Trait Endoscopy, CDI (Centro Diagnostico Italiano), Milan, Italy.
4. 4Epidemiology and Biostatistics Unit, Istituto Nazionale Tumori - IRCCS - Fondazione G. Pascale, Napoli, Italy.
5. 5Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy.