Prognostic Heterogeneity Between Oral Tongue and Gingivobuccal Tumours Based on Lymph Node Ratio and Number of Positive Nodes: A Survival Analysis.

ABSTRACT

Introduction: Lymph node ratio (LNR) and number of pathological positive nodes (pN) have shown better prognostic prediction compared to laterality, size and number of nodes (single or multiple). This study evaluates the prognostic significance of LNR and the number of  pathological positive nodes in predicting the outcomes of node positive oral squamous cell carcinoma(OSCC). It attempts to assess the prognostic heterogeneity between oral tongue and gingivobuccal complex tumours based on the lymph node ratio and the number of pathological positive nodes. Materials and Methods: A retrospective chart review of 498 previously untreated OSCC patients from January 2014 to December 2017 at our tertiary cancer institute was done. Our analysis included 133 oral tongue and 79 gingivobuccal tumours with histopathologically proven lymph node metastasis. The impact of LNR and number of positive nodes on overall survival and disease free survival was studied. Results: Overall survival rate was found to vary significantly based on LNR (> 0.06) and number of positive nodes (> 2). Overall survival reduced significantly in GBC tumours when LNR was more than 0.06(63.37 vs 32.1, p 0.005) but the same trend was not seen with tongue cancers (55.61 vs 41.9, p 0.98). Both the groups shown no difference in DFS based on LNR. Overall survival reduced significantly in both the groups when >2o pathologically positive nodes were present but disease free survival did not vary significantly in both the groups. Conclusion: Lymph node ratio (> 0.06) and number of pathological positive nodes (> 2) provide a better prognostic stratification in node positive oral squamous cell carcinoma. Oral tongue and GBC tumours were found to have a differential impact on overall survival rate on the stratification based on LNR.