The Value of Total Lymph Nodes Examined and Number of Positive Lymph Nodes in Determining the Role of Adjuvant Radiation in Pancreatic Cancer Patients.

Objectives: The aim of this study was to determine the survival benefits by adjuvant radiation therapy (RT) in pancreatic cancer patients with different total lymph nodes examined (TNE), number of positive lymph nodes (NPN), and lymph nodes ratio (LNR).

Methods: National Cancer Database was queried for nonmetastatic pancreatic cancer patients from 2004 to 2015. Cox models were utilized. Interaction terms were applied to evaluate the effect of RT in different NPN, LNR, and margin strata. Multivariate analysis was performed.

Results: Of 19,759 patients identified, 10,910 patients qualified. Compared with TNE of 1 to 9, TNE of 10 to 14, 15 to 19, 20 to 24, and 25 or greater had progressive overall survival (OS) benefits. Adjuvant RT had similar OS benefits among them. In negative margin patients, adjuvant RT improved OS when NPN was 2 to 3 (hazards ratio [HR], 0.84; P = 0.01) or LNR was 0.15 to 0.25 (HR, 0.79; P = 0.002). In positive margin patients, adjuvant RT nonsignificantly improved OS when NPN was 1 to 3 (HR, 0.89; P = 0.36) or when NPN was 4 or greater (HR, 0.79; P = 0.07).

Conclusions: Higher TNE correlates with better survival. Adjuvant RT may not compensate for inadequate lymph node dissection. Adjuvant RT improves survival in negative-margin patients with 2 to 3 positive lymph nodes or LNR of 0.15 to 0.25.