Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Background: Oral cavity squamous cell carcinoma (OCSCC) constitutes over 90% of oral cancers and is associated with high morbidity and mortality, particularly when lymph node metastasis (LNM) is present. Elective neck dissection (END) is the current gold standard for staging the neck when the depth of invasion (DOI) exceeds 4mm, but is considered for DOI between 2-4mm. The DOI threshold where an END is associated with improvement in overall survival (OS) has been incompletely analyzed in a national dataset.
Objective(s): Our primary objective was to identify the DOI threshold where END is associated with an improvement in OS. A secondary objective was to identify differences in OS between a high-quality neck dissection (HQND, >18 lymph nodes removed) versus elective neck dissection (<18 lymph nodes removed) or observation.
Methods: We performed a retrospective analysis of all subjects diagnosed with a T1 or T2 N0 OCSCC who underwent resection with or without END between 2010-2017 using the 2021 Patient User File of the National Cancer Database (NCDB). Subjects with grossly positive margins, distant metastatic disease, and missing data were excluded. OS was calculated via Kaplan Meier method. Cox proportional hazards models were used to evaluate the association of clinical variables with OS. Multivariable models were created to adjust for known confounders. Adjusted hazard ratios (ratios (aHR) with associated 95% confidence intervals (CI) were generated comparing observation and END to HQND.
Results: 9350 subjects fit inclusion criteria. 996 underwent observation, 2,497 underwent END, and 5857 underwent HEND. In the overall cohort, END was associated with an 18% increase in mortality odds (aHR 1.18, 95% CI: 1.09-1.27) while observation had a 48% increase in mortality odds (aHR 1.48, 95% CI: 1.32-1.65) compared to HQND. Observation in T1 tumors had 34% increased mortality odds compared to HEND (aHR 1.34, 95% CI: 1.15-1.58) while observation in T2 tumors had a 57% increase compared to HEND (aHR 1.57, 95% CI: 1.38-1.82). There was a significant difference in odds of mortality between END versus HQND for T2 tumors (aHR 1.24, 95% CI: 1.13-1.36), however this was not present in T1 tumors (aHR 1.06, 95% CI: 0.92-1.22). The DOI threshold where reduction in OS was seen with observation versus HQND was ≥3mm (aHR 1.48, 95% CI: 1.32-1.65). At this cutoff, a significant increase in mortality odds was also noted in END compared to HQND (aHR 1.18, 95% CI: 1.09-1.27).
Conclusion: This national analysis demonstrates that patients with OCSCC have improved OS following HQND when compared to observation, when the tumor DOI reaches 3mm. This analysis also demonstrated an improvement in OS when lymph nodal count during END exceeds 18 lymph nodes.
Keywords: Depth of invasion, oral cavity squamous cell carcinoma, high-quality neck dissection, elective neck dissection, overall survival, National Cancer Database