1. Department of General and Digestive Surgery, Hospital Universitario Ramón y Cajal, 28034 Madrid, Spain
2. Instituto Ramón y Cajal de Investigación Sanitaria, IRyCIS, Hospital Universitario Ramón y Cajal, 28034 Madrid, Spain
3. Faculty of Medicine, University of Alcalá (UAH), Alcalá de Henares, 28801 Madrid, Spain
4. Department of General and Digestive Surgery, Hospital Universitario La Paz, 28046 Madrid, Spain
5. Department of Clinical Oncology, Hospital Universitario Ramón y Cajal, 28034 Madrid, Spain
6. Department of Endocrinology and Nutrition, Hospital Universitario Ramón y Cajal, 28034 Madrid, Spain