Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are tumors derived from neuroendocrine cells thatcan occur anywhere along the gastrointestinal tract. Due totheir particular features, GEP-NETs are among the mostcomplex tumors to diagnose and treat. For instance,symptoms vary according to the type of GEP-NET, andtherefore they are easily mistaken for other conditions.Although the general idea is that GEP-NETs are raretumors, the most recent data from the US SurveillanceEpidemiology and End Results show an impressiveincrease of more than 400% in the incidence of this diseaseover a period of 29 years, rising from 1.09 per 100,000population in 1973 to 5.25 per 100,000 population in 2004[1]. Only in the last year, their incidence increase from 3.00to 5.25 per 100,000. In fact, GEP-NETs are more prevalentthan many other tumors of the gastrointestinal tract,including stomach and pancreatic carcinomas combined.Survival of patients with GEP-NETs depends greatly onstage and histology. For example, patients with well andmoderately well-differentiated distant metastases have a 5-yearsurvivalprobabilityof35%;conversely,inpatientswithpoorlydifferentiateddistantmetastases,the5-yearsurvivalprobabilitydrops to only 4% [ 1]. The mere observation of these figurescalls our attention to the importance of an early diagnosis, andtumor classification and staging of patients in whom a GEP-NET is suspected, as well as to the need for ongoingmodifications in the therapeutic approach.Interestingly, in parallel to changes in the epidemiologyof GEP-NET, there have been substantial advances intreatment, such as the use of peptide receptor radiotherapy,and more recently, antiangiogenic agents (bevacizumab,everolimus, sunitinib), which have echoed on the prognosisof many patients with this disease. As shown by the resultsof the RADIANT trials, with the advent of targetedtherapies, we may be on the verge of a paradigm shift inthe treatment of advanced GEP-NETs.The Spanish Group of Neuroendocrine Tumors(GETNE), aware of the interest this disease has raised dueto its increasing incidence and significant advances intreatment, considered it would be of relevance to publishthe contents from the“V GETNE Symposium on GEP-NETs” held in September 2009 in the city of Madrid(Spain). In this Special Issue, the updated contents of thissymposium are reported. The purpose is to provide ageneral overview of the current state of knowledge of GEP-NETs regarding diagnosis and innovations in therapy.Reference