Influence of Site, Size, Depth of Invasion and Histologic Grading on the Occurrence of Cervical Level IIb Metastasis and Extranodal Extension in Clinically N0 Neck of Patients with OSCC: A Single Center Retrospective Analysis.

Background: Depth of Invasion ≥ 4 mm, T stage and primary site with more than 20% chances for occult metastasis are currently the accepted indications for elective neck dissection. Nodal metastasis decreases survival by 50%. ENE further reduces the prognosis. Dissection of level IIb lymph nodes in clinically N0 neck does not improve survival. Methods: A total of 320 patients were evaluated. Binary and multiple logistic regression and chi-square test were used for data analysis. ROC curve with Youden's J index was used to set up a cutoff value for DOI. The predictor variables were site, size, grading and depth of invasion of primary tumor. Incidence of level IIb metastasis and ENE were the outcomes. Results: The study revealed a significant association and risk stratification between primary tumor characteristics with the occurrence of ENE. The cutoff value for DOI predicting ENE was 12.5 mm. Tumors of the oral tongue were an independent risk factor for level IIb metastasis. Discussion: Size of primary tumor, DOI, tumors of the mandibular alveolus and poor grading are independent risk factors for ENE. Isolated metastasis to level IIb rarely occurs in the absence of concomitant level IIa metastasis. Size, DOI and grading were significantly associated with level IIb metastasis. However, only tumors of the oral tongue were independent risk factor.