When is neoadjuvant chemotherapy indicated in rectal neuroendocrine tumors? An analysis of the National Cancer Database.

Abstract

e15631 Background: Rectal neuroendocrine tumors (rNET) are rare and challenging to manage. While most patients with small rNET can be definitively treated with local excision, the role of chemotherapy in general and neoadjuvant therapy specifically in managing advanced rNET has not been well established. Therefore, this study aimed to determine which patients with rNET may gain a survival benefit from neoadjuvant chemotherapy. Methods: A retrospective cohort analysis of all patients who underwent surgical resection of rNET in the US National Cancer Database (NCDB) (2004-2019) was performed. First, univariate and multivariate cox regression analyses were performed to determine the independent predictors of poor overall survival (OS) and define the high-risk groups. Afterwards, stratified OS analyses were performed for each high-risk group to assess whether neoadjuvant chemotherapy had a survival benefit in each group. Results: 1837 patients (49.8% female; mean age 56.6 ±12.3 years) underwent radical resection of a rectal neuroendocrine tumor. Tumors > 20 mm in size, clinical T4 tumors, poorly differentiated tumors, and metastatic disease were independent predictors of worse OS and were defined as high risk groups. Neoadjuvant chemotherapy did not have a significant survival benefit in any of the high-risk groups, except for patients with high-grade rNETs where neoadjuvant therapy significantly improved OS to a mean of 30.9 months compared to 15.9 months when neoadjuvant therapy was not given (p = 0.006). Conclusions: Neoadjuvant chemotherapy improved OS of patients with high-grade rNET by 15 months and may be indicated for this group.