Carcinoid Tumors of the Gastrointestinal Tract and Associated Carcinoid Syndrome: A Population-Based Study

Introduction: Carcinoid tumors are slow-growing neuroendocrine malignancies that classically originate from either the gastrointestinal (GI) tract or pulmonary system, of which the GI subtype is most common (70%). Embryonically, these GI tumors originate from neuroectoderm argentaffin cells found in the mucosa at the base of the crypts of Lieberkuhn. The aims of this study were to describe the demographics of the population and describe predict the factors associated with the development of carcinoid syndrome. Methods: Retrospective analysis of National Inpatient Sample (NIS) discharge data from January 2004 to December 2009 was performed. International Classification of Diseases, Ninth revision, Clinical Modifications (ICD-9-CM) codes were used to identify discharges with a primary diagnosis of carcinoid tumors (CNT). Results: During the study period, the total number of hospital discharges for CNT were 2,135. Small bowel carcinoids (SBCNT) accounted for 55% of the cases, with 53% originating in the illeum, 15% in the duodenum, and 7% in the jejunum. Only 45% of the CNT cases originated from the colon (CCNT); 45% were from the appendix, 17% in the cecum, 7% from the ascending colon, 1.5% from the transverse, <1% in the descending colon, 4% in the sigmoid colon, and 17% in the rectum. Approximately 79% of the SBCNT cases were malignant versus 70% of cases with CCNT. While males had a larger proportion of SBCNT (52%), females had a significantly higher proportion of CCNT (57%). Average age of presentation with SBCNT was 62 years and for CCNT was 54 years. Seventy percent of Caucasians were diagnosed with CNT, and higher SES patients tend to have a higher proportion of CCNT. A higher proportion of cases with CCNT did not have metastasis (78%) when compared with SBCNT (62%). While this was significantly different, both had similar proportion of metastasis to the lymph node, liver, peritoneum, and bone. Among cases with SBCNT, only 12% presented with carcinoid syndrome when compared with 7% among CCNT cases. The odds ratio (OR) of developing carcinoid syndrome was higher among SBCNT OR=1.58, malignant tumors OR=1.968, and metastatic tumors OR=1.485 when compared to CCNT. Conclusion: Carcinoid tumors are rare tumors. Patients who present to the hospital are more likely to have SBCNT and are older. Females have a higher probability of having CCNT vs. SBCNT. There seems to be a link between higher SES and higher proportion of CCNT. A majority of SBCNT originated from the illeum, while the majority of CCNT originated from the appendix and cecum. Carcinoid syndrome seems to be a marker for malignant CCNT with metastatic disease.