1 Department of Biostatistics EA 2694, University Hospital of Lille, Lille, France University of Lille---Nord de France, Lille, France SIRIC ONCOLille, Rue Polonovski, Lille Cedex, France Department of Biostatistics EA 2694, University Hospital of Lille, Lille, France University of Lille---Nord de France, Lille, France Department of Digestive and Oncological Surgery, University Hospital of Lille, Lille, France University of Lille---Nord de France, Lille, France Department of Digestive and Oncological Surgery, University Hospital of Lille, Lille, France SIRIC ONCOLille, Rue Polonovski Lille Cedex, France.