Can Metastatic Lymph node ratio be used as an independent prognostic factor in Carcinoma tongue?

Background: Lymph node metastasis is an established prognostic factor in carcinoma of tongue. The association between lymph node ratio (LNR, the ratio of positive lymph nodes to the total number of dissected lymph nodes) and survival has been recently studied. But the available literature is mostly retrospective in nature and they take the broad group of oral squamous cell carcinoma as a whole and not as a single sub-site; also it does not take in to consideration the importance of standardising the minimum number of lymph nodes to be dissected or a single head and neck pathologist examining the specimen to avoid wide variations in the ratio and to reduce the bias. Hence we sought to determine using a prospective study whether the lymph node ratio, as an independent factor impacts survival in node-positive squamous cell carcinoma of tongue and whether a cut-off can be arrived at to risk stratify the patients.

Methods: We prospectively studied 51 consecutive pathologically node positive patients with squamous cell carcinoma tongue who satisfied our selection criteria. A standard surgery for the primary was done under frozen control and a comprehensive neck dissection, with the minimum number of lymph node harvest kept at 15. All the specimens were examined by a single head and neck pathologist. Further adjuvant treatment was given according to our institution protocol. They were followed up with a regular clinical examination for an average period of 24 months. The 2 Yr OS and DFS were calculated using the Kaplan Meier method. LNR was subjected to univariate and multivariate analyses.

Results: The 2 yr OS was 37.8% for patients with LNR>0.10 compared with 88.2% for patients with LNR <0.10 (p value=0.0187).Similarly, the DFS was 46.3% for patients with LNR >0.10compared with 83.6% for those with LND<0.10 (p value=0.0859).LNR was a significant prognostic factor in both univariate and multi variate analyses.

Conclusion: In squamous cell carcinoma of tongue, an increased Lymph node ratio (LNR) is a strong predictor of decreased survival. A lymph node ratio (LNR)>0.10 is associated with a worse outcome.