Lymph node ratio as prognostic variable in oral squamous cell carcinomas: Systematic review and meta-analysis

Lymph node ratio (LNR) has been shown to be an independent prognostic factor for oral squamous cell carcinoma (OSCC) in various centre-based studies recently. A range of cut-off values have been suggested. A meta-analysis was performed to evaluate the prognostic effects of LNR and to investigate the cut-off value. Electronic search on Pubmed, Embase and Cochrane library and manual search were performed for studies up to January 2018. The outcomes were overall survival (OS), disease specific survival (DSS), disease free survival (DFS), local recurrence free survival (LF), locoregional disease free survival (LRF), and distant metastasis disease free survival (DM). 19 studies between 2009 and 2017 were included. The total number of patients was 14,254 (range 19-3958). Data was grouped into Group A (with pathological nodal disease, pN+) and Group B (with and without pathological nodal disease, pN+ and pN-). In the meta-analysis, the high LNR was significantly related to short OS (A = HR 1.902; 95% CI: 1.453-2.488, B = HR 2.76; 95% CI: 2.13-3.59), DSS (A = HR 1.728; 95% CI: 1.159-2.579; B = HR 2.83; 95% CI: 1.8-4.44) and DFS (A = HR 2.27; 95% CI: 1.74-2.96; B = HR 2.01; 95% CI: 1.44-2.82) in both groups; and shorter LRF in Group B (HR 5.013; 95% CI: 3.584-7.011). In the analysis, all cutoff values were shown to be significant and there was no strong evidence to consider a possibility of a second significant value. Based on our results, LNR is an independent prognostic factor in OSCC and may be considered in future oncologic staging systems.