Neuroendocrine Tumors of the Gastrointestinal System

Introduction: Neuroendocrine tumors (NETs) of the gastrointestinal tract arise from the extensive serotonergic entero-endocrine system. There is very limited literature focusing on risk factors for development and progression of these tumors. Therefore, this retrospective study aims to compare large bowel, small bowel and stomach neuroendocrine tumors based on disease presentation, tumor progression and associations with certain lifestyle habits and/or the use of drugs that have the potential to modulate the neuroendocrine system. Materials and Methods: We identified 56 patients at the Michael E. DeBakey Veterans Affairs Medical Center (Houston, TX) from 2000 to 2010. Patients were considered eligible if they were at least 21 years old with established treated or untreated primary gastrointestinal NETs. Relevant demographic factors and clinical history was obtained for all patients. Additionally, use of a broad range of medications directly or potentially affecting the serotonergic system was documented. Results and Discussion: The majority of NETs were in the large bowel (n = 32), followed by small bowel (n = 20) and stomach (n = 4). Small bowel NETs showed a higher propensity to metastasize than large bowel or stomach tumors (p = 0.002). Conversely, there was a significant association between smoking and development of large bowel NETs (p = 0.04). No significant association with medication use was observed. Conclusion: NETs within the small bowel have more aggressive clinical courses and may warrant more extensive initial evaluations. Furthermore, our data further supports the association between smoking and development of neuroendocrine tumors, particularly of the large bowel.