In this meta-analysis, we aimed to evaluate the prognostic implication of the metastatic lymph node ratio (mLNR) and its optimal criterion in pancreatic ductal adenocarcinoma (PDAC) with lymph node metastasis (LNM). The present study included 3735 patients with PDAC who had LNM, from 11 eligible studies. We carried out a meta-analysis to determine the correlation between a high mLNR and PDAC prognosis. The estimated mean numbers of examined and metastatic lymph nodes were 22.396 (95% confidence interval [CI] = 19.681-25.111) and 6.496 (95% CI = 4.646-8.345), respectively. A high mLNR was significantly correlated with worse overall survival (hazard ratio = 1.344, 95% CI = 1.276-1.416). In 3 subgroups based on high mLNR criteria (>0 and <0.2, ≥0.2 and <0.4, and ≥0.4), there were significant correlations between a high mLNR and worse survival. A cutoff of 0.200 showed the highest hazard ratio (1.391, 95% CI = 1.268-1.525), which was statistically significant. Our results showed that mLNR is a useful prognostic factor for PDAC with LNM. Although the optimal criterion of high mLNR may be 0.200, further cumulative studies are required before this can be applied in daily practice.
Keywords: lymph node metastasis; meta-analysis; metastatic lymph node ratio; pancreatic ductal adenocarcinoma; prognosis.