The association of lymph node yield and survival after neoadjuvant immunotherapy for head and neck cancer: An NCDB analysis.

e18120 Background: Comprehensive lymph node resection is a quality measure previously associated with survival for head and neck squamous cell carcinoma (HNSCC); however, the prognostic significance of nodal yield after neoadjuvant immunotherapy is an important unanswered question for clinical management and trial development. This study evaluated the association of lymph node yield with overall survival (OS) among patients with HNSCC who underwent neoadjuvant immunotherapy. Methods: The US National Cancer Database (2004-2022) was queried for HNSCC patients who underwent neoadjuvant immunotherapy followed by surgical resection. 1:1 matched non-neoadjuvant controls were created using demographic variables, facility, stage, lymphovascular invasion, and year. Positive lymph node percentage (malignant lymph nodes/total lymph nodes resected) was assessed. Cox proportional hazard models identified prognosticators of five-year OS. Results: The study included 462 patients who received neoadjuvant immunotherapy and 462 matched controls. Median age was 60 years [IQR 53-67] and 74.5% were male. The majority (53.5%) had stage IV disease and received adjuvant radiation (72.7%). Compared to non-neoadjuvant controls, those who received neoadjuvant immunotherapy had more lymph nodes (median [IQR] 43 [31-60] vs 29 [18-45] P<0.001), but a similar percentage of positive nodes (2.5% [0.0%-7.1%] vs 3.1% [0.0%-8.8%], P=0.09). Total number of nodes removed did not predict survival in the neoadjuvant immunotherapy group. Positive lymph node percentage predicted 5-year OS, with every one-percent increase in positive lymph nodes resulting in increased hazard of death by 1.4% (HR: 1.014, 95% CI: 1.006, 1.023) and 1.6% (HR: 1.016, 95% CI: 1.010, 1.030) in unadjusted and adjusted models, respectively. Conclusions: In patients with head and neck cancer treated with neoadjuvant immunotherapy, lymph node yield is not associated with improved survival. Prospective studies are required to determine if typical quality metrics for lymph node yield apply to patients treated with neoadjuvant immunotherapy.