Re-examining predictors of pathologic lymph node positivity in clinically node negative oral cavity cancer.

BACKGROUND: Elective lymph node dissection (ELND) is performed for many early-stage oral cavity squamous cell carcinomas (OCSCC) with clinically negative necks (cN0), often guided by depth of invasion (DOI). However, DOI is less validated in non-tongue OC sites, and often correlates with other adverse features. We sought to evaluate the utility of DOI versus other factors for independently predicting pathologic lymph node positivity (pN+) in patients with cN0 OCSCC. METHODS: Patients with cN0 OCSCC diagnosed from 2010 to 2015 undergoing primary surgery were identified in the National Cancer Data Base. RESULTS: 5060 cN0 OCSCC patients met inclusion criteria. The presence of lymphovascular invasion (LVI) was the strongest independent predictor of pN+ (odds ratio [OR] = 4.27, 95% confidence interval [CI] 3.36-5.42, P < 0.001). High histologic grade also strongly predicted pN+ (OR 3.33, 95% CI 2.20-4.60, P < 0.001). DOI had no association with the likelihood of pN+ among all OCSCC patients, but was predictive among patients within the oral tongue subset (OR 2.01, 95% CI 1.08-3.73, P = 0.03 for DOI > 20 mm vs. DOI: 2.0-3.99 mm). CONCLUSION: LVI and grade are the strongest independent predictors of pN+ in cN0 OCSCC. Contrary to prior studies, DOI was not found to be a predictor of pN+ among patients with cN0 OCSCC. However, DOI was a predictor of pN+ or the oral tongue subset, albeit still less strongly than LVI or grade. These findings could potentially be used to better identify a subset of cN0 OCSCC patients who could be considered for omission of ELND in future studies.