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Session:: ePosters-Mon330-M6: Colon & Colorectal Cancer

EP1071 - Right- versus Left-Sided Colon Neuroendocrine Tumors: An Analysis of Clinicopathological Differences and Survival Outcomes

Monday, May 11, 2026
4:30 PM - 4:35 PM ET

    ePoster Presenter(s)

  • Marc M. Mankarious, MD

    General Surgery Resident
    Penn State Milton S Hershey Medical Center
    Herhsey, PA, United States

    Disclosure information not submitted.

    • Author(s)

  • Austin Portolese, MD

    General Surgery Resident
    Penn State Health
    Pennsylvania State University College of Medicine
    Hershey, PA, United States

    Disclosure information not submitted.

  • Eustina G. Kwon, MD MPH (she/her/hers)

    Resident
    Penn State Health
    Penn State Health
    Hershey, PA, United States

    All of the relevant financial relationships listed below have been mitigated.
    This individual has no financial relationships with ineligible companies.

  • HC

    Heather Carmichael, MD

    Assistant Professor
    Department of Surgery, Division of Colon and Rectal Surgery
    Hershey, Pennsylvania, United States

    Disclosure information not submitted.

  • AK

    Audrey S. Kulaylat, MD MSc

    Assistant Professor
    Penn State Health
    Hershey, Pennsylvania, United States

    Disclosure information not submitted.

  • JS

    Jeffrey S. Scow, MD, FACS, FASCRS

    Associate Professor of Surgery
    Milton S. Hershey Medical Center, Penn State Health
    Hershey, Pennsylvania, United States

    Disclosure information not submitted.

    • Senior Author(s)

  • PL

    Patricio B. Lynn, MD

    Assistant Professor of Surgery
    Penn State University
    Hummelstown, Pennsylvania, United States

    All of the relevant financial relationships listed below have been mitigated.
    This individual has no financial relationships with ineligible companies.

All of the relevant financial relationships listed below have been mitigated.
Eustina G. Kwon, MD MPH: This individual has no financial relationships with ineligible companies.
Patricio B. Lynn, MD: This individual has no financial relationships with ineligible companies.
Purpose/Background: Differences in tumor biology and clinical outcomes between left- and right-sided colorectal adenocarcinomas are well-established. However, there is a paucity of data on whether this anatomical distinction influences the prognosis of colon neuroendocrine tumors (CNETs). This study aims to investigate the differences in clinicopathological characteristics and overall survival between right-sided and left-sided CNETs using a large national database.

Methods/Interventions: We conducted a retrospective cohort study using the National Cancer Database (NCDB) for the years 2004-2023. Patients with a primary histological diagnosis of neuroendocrine tumor of the colon were identified. Tumors located from the cecum to the splenic flexure were classified as right-sided, while those in the descending and sigmoid colon were classified as left-sided. Patients with appendiceal tumors or unknown primary sites were excluded. Baseline patient and tumor characteristics were compared using univariate analysis. Overall survival was analyzed using the Kaplan-Meier method, and multivariable logistic regression was performed to identify independent predictors of survival. A p-value of < 0.05 was considered statistically significant for all values presented.

Results/Outcomes: A total of 6,471 patients with CNETs were identified, with 5,377 (83%) having right-sided and 1,094 (17%) having left-sided tumors. Distribtuion of tumors by primary site shown in Figure 1. Compared to patients with left-sided tumors, those with right-sided tumors were significantly older (median 66 vs. 62 years, p< 0.05), more likely to be female (52.5% vs. 46.0%, p< 0.05), and more frequently presented at stage IV (53.6% vs. 48.4%, p< 0.001) and with lymphovascular invasion (35.1% vs. 19.9%, p< 0.001). Kaplan-Meier analysis revealed that patients with right-sided tumors had improved median overall survival in stages III (89 vs. 20 months, p< 0.05) and IV (6.5 vs. 4.7 months, p< 0.05), but a lower overall survival in stage I (114.8 vs. 179.3 months, p< 0.05). No significant difference was observed in stages II disease (Figure 2). On multivariable analysis, right-sided tumors were associated with improved overall survival (HR 0.85, p< 0.05). Predictors of worse overall survival included undifferentiated tumor grade (HR 4.31, p< 0.05), stage 4 disease (HR 3.4, p< 0.05)

Conclusion/Discussion: Our findings demonstrate significant clinicopathological and prognostic differences between right- and left-sided CNETs. Despite presenting with more advanced features, right-sided tumors were associated with better survival outcomes in later stages. Tumor sidedness appears to be an independent prognostic factor in CNETs, highlighting the importance of primary tumor location in risk stratification and clinical management of these rare malignancies.

Figure 2: Overall Survival in Colonic Neuroendocrine Tumors by Tumor Side and Separated by Disease Stage
Figure 2: Overall survival in patients with colonic neuroendocrine tumors. Cohorts represent right-sided vs. left-sided in A) Stage I disease; B) Stage II disease; C) Stage III disease; D) Stage IV disease
Figure 1: Distribution of Colon Neuroendocrine Tumors by Primary Site
Figure 1: Pie chart depicting primary site distribution of colon neuroendocrine tumors in National Cancer Database (NCDB) from 2004-2023.