Mixed adenoneuroendocrine carcinomas of the appendix: Is there a survival advantage to right hemicolectomy over appendectomy?

Background

the surgical treatment and prognostic characteristics of mixed adenoneuroendocrine carcinomas (MANEC) of the appendix are not yet available. In this study, we sought to figure out the choice of surgical approach (right hemicolectomy versus appendectomy), and explore the effect of chemotherapy on appendiceal MANEC.

Methods

patients with appendiceal MANEC from the Surveillance, Epidemiology, and End Results database (2000–2020) were stratified by gender, race, age group, tumor grade, and TNM stage. Logistic regression and Kaplan-Meier analyses relating TNM stage, grade, and receipt of right hemicolectomy (abbreviated as colectomy) to overall and cancer-specific survival were performed.

Results

455 patients with appendiceal MANEC were included, of whom 146(32 %) underwent appendectomy and 309(68 %) underwent colectomy. Patients who underwent colectomy had better cancer-specific survival (HR = 0.68, 95%CI (0.47–0.98), P = 0.041) and overall survival (HR = 0.67, 95%CI (0.48–0.93), P = 0.015) than those who underwent appendectomy alone. However, colectomy did not confer any survival advantage over appendectomy in subgroup analyses, including low-grade or high-grade tumors, T1-2N0M0 group, T3-4N0M0 group, node-positive non-metastatic tumors, and metastatic tumors. On multivariate analysis, lack of chemotherapy and high-stage (node-positive or metastatic) were associated with poorer overall survival; high-grade (grade 3–4) and high-stage were primary predictors of cancer-specific mortality. Furthermore, there was no significant association between colectomy and better survival, either overall survival or cancer specific survival, when accounting for tumor stage and grade.

Conclusions

Our study found that colectomy did not provide a survival benefit compared to appendectomy alone. Moreover, tumor stage and grade were independent determinants of cancer specific survival; chemotherapy and tumor stage were independent determinants of overall survival.