A critical evaluation of lymph node ratio in head and neck cancer

In head and neck squamous cell carcinoma (HNSCC), the search for better prognostic factors beyond TNM-stage is ongoing. Lymph node ratio (LNR) (positive lymph nodes/total lymph nodes) is gaining interest in view of its potential prognostic significance. All HNSCC patients at the Netherlands Cancer Institute undergoing neck dissection for lymph node metastases in the neck region between 2002 and 2012 (n = 176) were included. Based on a protocol change in specimen processing, the cohort was subdivided in two distinct consecutive periods (pre and post 2007). The prognostic value of LNR, N-stage, and number of positive lymph nodes for overall survival was assessed. The mean number of examined lymph nodes after 2007 was significantly higher (42.3) than before (35.8) (p = 0.024). The higher number concerned mostly lymph nodes in level V. The mean number of positive lymph nodes before 2007 was 3.3 vs. 3.6 after 2007 (p = 0.745). By multivariate analysis of both pre- and post-2007 cohort data, two factors remained associated with an increased hazard of dying: N2 [HR 2.1 (1.1-4.1) and 2.4 (1.0-5.8)] and >3 positive lymph nodes [HR 2.0 (1.1-3.5) and 3.1 (1.4-6.9)]. Hazard ratio for LNR >7 % was not significantly different: pre 2007 at 2.2 (1.3-3.8) and post 2007 at 2.1 (1.0-4.8, p = 0.053). In this study, changes in specimen processing influenced LNR values, but not the total number of tumor positive nodes found. Therefore, in HNSCC, the number of positive nodes seems a more reliable parameter than LNR, provided a minimum number of lymph nodes are examined.