1. Department of General Surgery Clínica Universidad de Navarra, University of Navarra Pamplona Spain
2. Institute of Health Research of Navarra (IdisNA) Pamplona Spain
3. Department of Oncology University Hospital of León Leon Spain
4. Department of General Surgery University Hospital of León Leon Spain
5. Department of General Surgery University Hospital Gregorio Marañón Madrid Spain
6. Department of General Surgery University Hospital Río Hortega Valladolid Spain
7. Department of Oncology, Clínica Universidad de Navarra University of Navarra Pamplona Spain
8. Department of General Surgery, Clínica Universidad de Navarra University of Navarra Madrid Spain