EP590 - Clinicopathologic Differences and Outcomes Between Right Hemicolectomy and Appendectomy for high-risk Appendiceal Carcinoid Tumors: A Retrospective Institutional Analysis

Purpose/Background: Right hemicolectomy (RHC) is traditionally recommended for appendiceal neuroendocrine tumors (ANETs) ≥2 cm or with high-risk features, yet optimal management of intermediate-sized (1-2 cm) remains controversial. These "gray zone" tumors display heterogeneous behavior, and evidence regarding the benefit of RHC in this subgroup is conflicting. This study aims to compare clinicopathologic variables, adjuvant treatment modalities, and outcomes between patients undergoing right hemicolectomy versus appendectomy for appendiceal carcinoids size between 1 and 2 cm at a single institution.

Methods/Interventions: A retrospective cohort study was conducted utilizing the North American Association of Central Cancer Registry (NAACCR) dataset. We identified 73 patients with histologically confirmed ANETs between the size of 1-2 cm with high-risk features treated by appendectomy (N=60) vs. RHC (n=13). Demographics, tumor stage, lymphovascular and perineural invasion, adjuvant therapy, recurrence, and mortality were compared using ANOVA, chi-square, and t-tests, with significance set at p < 0.05.

Results/Outcomes: Patients undergoing right hemicolectomy were significantly older (mean 54.9 ± 17.4 years) than those treated with appendectomy (43.6 ± 17.5 years, p = 0.037). There were no significant differences in sex distribution, race, or BMI (mean 28.2 ± 4.5). Advanced stage disease (Stage III) was more frequent in the RHC group (46.2% vs 16.7%), while Stage I tumors predominated after appendectomy (48.3%, p = 0.081). Rates of lymphovascular invasion (4.1%) and perineural invasion (20.5%) were similar between groups. Surgical margins were negative in 98.6% of cases. Adjuvant chemotherapy was administered more often after right hemicolectomy (23.1% vs 1.7%, p = 0.016), yet recurrence and mortality outcomes were comparable. Recurrence occurred in only 2 patients (2.7% overall), while mortality was 15.4% in the hemicolectomy group versus 3.3% following appendectomy (p = 0.143).

Conclusion/Discussion: Despite greater use of adjuvant therapy and more advanced staging in the right hemicolectomy group, long-term recurrence and survival outcomes were similar between surgical strategies. These findings suggest that appendectomy alone provides adequate oncologic control for most appendiceal carcinoid tumors ≤2 cm, even in the presence of limited high-risk features. Further multicenter or prospective analyses are warranted to refine surgical guidelines and identify subgroups that may benefit from extended resection.

Patient Characteristics and Outcomes of RHC vs. appendectomy for high risk appendiceal carcinoids
Patient Characteristics and Outcomes of RHC vs. appendectomy for high risk appendiceal carcinoids (Continued)