Prognostic significance of lymph node yield and lymph node ratio in patients affected by squamous cell carcinoma of the oral cavity and oropharynx: study protocol for a prospective, multicenter, observational study

Background: Lymph node involvement is a fundamental prognostic factor in head and neck squamous cell carcinoma (SCC). Lymph node yield (LNY), which is the number of lymph nodes retrieved after neck dissection, and lymph node ratio (LNR), which is the ratio of positive lymph nodes out of the total removed, are measurable indicators that may have the potential to be used as prognostic factors. The present study is designed to define the exact role of LNY and LNR regarding the overall and specific survival of patients affected by oral cavity and oropharyngeal SCC. It has been registered on clinicaltrials.gov database (NCT03534778). Methods: This is a multicenter study involving tertiary care referral centers in Europe and North America. Patients affected by oral cavity, HPV+ and HPV- oropharyngeal SCC undergoing neck dissection will be consecutively enrolled and followed-up for up to 5 years. Patients and disease characteristic will be properly recorded and centrally analyzed. The primary end-point is to define reliable cut off-values for LNY and LNR which may serve as prognosticators of survival. This will be achieved through the use of ROC curves. Secondary outcomes will be the Overall survival (OS), Disease Specific Survival (DSS), and Progression Free Survival Hazard Ratios (HR) at 2-, 3- and 5 years, which will be evaluated through the Kaplan-Meier method and the difference in survival attested by the log-rank test. Univariate and multivariate analysis will be performed to understand the association of various outcomes with LNY and LNR.