Lymph node ratio as valuable predictor in pancreatic cancer treated with R0 resection and adjuvant treatment

Background: Lymph-node (LN) metastasis is an important prognostic factor in resected pancreatic cancer. In this study, the prognostic value of American Joint Committee on Cancer (AJCC) 8th edition N stage, lymph-node ratio (LNR), and log odds of positive lymph nodes (LODDS) in resected pancreatic cancer was investigated. Methods: Between January 2005 and December 2017, there were 351 patients with pancreatic cancer treated with R0 resection and adjuvant therapy at Seoul National University Hospital. Relationships between the three LN parameters and overall survival (OS) and recurrence-free survival (RFS) were evaluated using a log-rank test and Cox proportional hazard regression model. Each multivariate-adjusted LN parameter was internally validated by bootstrap-corrected Harrell's C-index. Results: The mean duration from surgery to adjuvant therapy was 47.6 ± 17.4 days. In total, the median OS and RFS was 31.7 (95% CI, 27.2-37.2) and 15.4 (95% CI, 13.5-17.7) months. The three LN classification systems were significantly correlated with OS and RFS in log-rank tests and multivariate-adjusted models (all p < 0.05). When internally validated, LNR showed the highest discrimination ability in predicting OS and RFS (each C-index = 0.65). LNR also showed the highest C-index in subgroup analysis, classified by adjuvant therapy modality. LNR and the AJCC 8th edition LN classification system were significantly associated with loco-regional recurrence (p = 0.026 and p = 0.027, respectively). Conclusions: LNR, which showed the best prognostic performance and significant relationship with loco-regional recurrence, can help further stratify the patients and establish an active treatment plan.