Minimum number of lymph nodes to maximize survival in non-metastatic appendiceal adenocarcinoma

Introduction

In non-metastatic appendiceal adenocarcinoma, the relationship between the number of lymph nodes harvested and overall survival is unknown. The objective of this study was to determine whether the number of lymph nodes harvested impacts survival in patients with mucinous and non-mucinous appendiceal cancer.

Methods

Retrospective cohort analysis was conducted in patients who underwent surgery for appendiceal adenocarcinoma in the SEER database from 2000–2019. Exclusion criteria included patients without the number of regional nodes harvested/node positivity, missing survival data, stage IV disease, and certain subtypes of appendiceal tumors. The primary outcome was 10-year overall survival.

Results

A total of 1651 patients were identified, 1101 with mucinous and 550 with non-mucinous cancer. The majority of patients were male (54 %) and between the ages of 50–74 (52 %). Mean ± SD number of lymph nodes harvested was 17.04 ± 10.41. The ten-year survival rates for patients with mucinous appendiceal cancer were 43–74 % and 25–68 % for non-mucinous cancer, depending on AJCC stage. Multivariate Cox-regression analysis displayed that the number of lymph nodes harvested was an independent predictor of survival (p < 0.0001). The optimal threshold predicted by Cox-regression for maximal survival benefit was harvest of a minimum of 15 nodes for mucinous and 12 for non-mucinous cancer. Additionally, for mucinous cancer, per each additional 3 nodes harvested past 15, the 10-year risk of mortality decreased by 7 % (HR 0.93 (0.88 to 0.98), p < 0.001).

Conclusions

The number of lymph nodes harvested is an independent predictor of survival for patients with appendiceal adenocarcinoma. To maximize this survival benefit, a minimum of 15 regional lymph nodes must be harvested for mucinous and 12 for non-mucinous cancer.