The optimal number of lymph nodes to evaluate among patients undergoing surgery for gallbladder cancer: Correlating the number of nodes removed with survival in 6531 patients

The aim of the current study was to identify the minimum number and the optimal range of lymph nodes (LNs) to be examined among patients with gallbladder cancer (GBC).Between January 1, 2004, and December 31, 2015, patients with a diagnosis of GBC were identified in the National Cancer Database. A machine-based learning approach was used to identify the minimum number and range of LNs to evaluate relative to long-term outcomes.Among 6531 patients with GBC, median number of LNs evaluated was 2 (IQR:1-5); only 21.1% (n = 1376) of patients had 6 or more LNs evaluated. The median number of metastatic LNs was 0 (IQR: 0-1). On multivariable analysis, evaluation of 4 LNs was associated with a higher hazard of death (referent 4-7 LNs: 4 LNs, HR = 1.27, 95% CI, 1.16-1.40; P 0.001), whereas, patients who had 4 to 7 LNs and 7 LNs evaluated had comparable long-term mortality risk (HR = 1.10, 95%CI, 0.98-1.24; P = 0.11). There was no difference in the proportion of patients who had at least one metastatic LN identified per T category based on total number of nodes resected (all P 0.05).The overwhelming majority of patients did not have the American Joint Committee on Cancer (AJCC) recommended 6 total LN count . A machine-based learning approach identified evaluation of 4 to 7 LNs as the LN number associated with optimal staging and survival. While obtaining 6 LNs may be challenging, evaluation of at least 4 LNs may be a more appropriate threshold as this cut-off value was associated with optimal patient outcomes and staging.