Lymph node ratio as a predictor of outcome in patients with oropharyngeal cancer.

To evaluate the utility of lymph node ratio (LNR) as a potential prognostic predictor and to test whether LNR may be useful as a potential selection criterion for adjuvant treatment in patients with oropharyngeal squamous cell carcinoma (OPSSC). This retrospective study included 384 patients with regionally metastasized OPSCC who underwent primary surgery with or without adjuvant therapy from 1980 to 2010. LNR was calculated as the ratio of positive lymph nodes to the total number of lymph nodes removed during neck dissection. Statistical analysis using a Cox regression model was carried out. The 5-year disease-specific survival (DSS) was 73%. An individual LNR peak at 0.1 was closest to the median of 0.0909, and both were set as cut-off values. Patients in the group greater than median had a hazard ratio (HR) of 2.472 for a DSS event; this was close to an HR of 2.513 for LNR >0.1. In multivariate analysis, LNR showed a markedly stronger HR with regard to survival in comparison with the grouped pN classification. The covariate treatment modality did not meet the assumption of the Cox regression, and it was therefore not possible to comment reasonably on the issue of whether LNR could be a potential selection criterion for adjuvant treatment. Lymph node ratio is in itself a valuable additional prognostic factor for risk stratification. According to the current results, the most valuable LNR for OPSSC is expected to be located in the range from 0.09 to 0.1. Further investigations in large prospective trials will be required to allow evidence-based recommendations for treatment decisions based on the LNR.