1 Department of Epidemiology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy;. Electronic address: cristina.bosetti@marionegri.it.
2 Department of Health Sciences Research, Medicine and Medical Genetics, Mayo Clinic, Rochester.
3 Department of Gastrointestinal Medical Oncology, UT M.D. Anderson Cancer Center, University of Texas, Houston, USA.
4 Departments of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy.