Location of Neuroendocrine Tumors in the Small Bowel Does Not Affect Survival

Mathew Shanley

Data presented at the 10th North American Neuroendocrine Tumor Society (NANETS) Annual Symposium in Philadelphia concluded that while neuroencrone tumors (NETs) in the distal region of the small bowel are larger and more likely to be unifocal than tumors in the middle, there are no significant differences in progression-free survival (PFS) or overall survival (OS) between the two.

In the gastrointestinal tract (GI), the small bowel (SB) is the most typical site for NETs, which are a rare cancer type that originate in the body’s neuroendocrine cells. Most studies of SBNETs report the ileum as a common location, however, specific locations of these tumors have not been well-defined.

The primary objective of the study, conducted by the University of Iowa Neuroendocrine Tumor Program, was to review a surgical database of patients undergoing primary operations for SBNETs to determine tumor location, the incidence of multifocality, the length of the resected bowel, and the total small bowel length to better understand the anatomical considerations in the management of these patients.

In the study, a surgical NET database was evaluated and patients undergoing primary resection of SBNETs were established. All data reviewed came from patients who underwent resection by a single surgeon and the distance to the ligament of Treitz (LT), the ileocecal valve (ICV), total bowel length, and length of restricted specimen were all measured at the time of surgery. The small bowel was divided into 3 domains: proximal (<100 cm of LT), distal  ( < 100 cm of ICV), and middle (> 100 cm from both the LT and ICV).

Patients with multifocal tumors in both middle and distal domains were classified as middle-distal. Survival and other clinicopathologic characteristics were compared across groups.

Per study results, most SBNETs were multifocal and the most common location was within 100 cm of the ICV. The multitude of distal tumors in this cohort is consistent with previous results from studies of SBNET location, however, the incidence of multifunctionality was 59% higher than earlier studies have reported.

Increased density of enterochromaffin cells in the terminal ileum, different hormone levels, and bile salt resorption could all be responsible for distal predilection, however, further studies are required to form a concensus on the environemental and/or anatomical factors that favor distal placement of the tumors.

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Keck KJ, et al. The Distal Predilection of Small Bowel Neuroendocrine Tumors. Presented at the 10th NANETS Annual Meeting; Philadelphia PA; October 20 – 22, 2017.
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