Lymph Node Yield and Ratio in Selective and Modified Radical Neck Dissection in Head and Neck Cancer—Impact on Oncological Outcome

SIMPLE SUMMARY: Head and neck cancers metastasize into the neck lymph nodes. The surgical removal of neck lymph nodes (i.e., neck dissection) is commonly performed before or after radiation therapy. The most common types of neck dissection include selective (with removal of nodes at risk) and radical modified (with removal of all neck lymph nodes). Given the variability in surgical techniques, quality and prognostic markers for neck dissection are missing. Lymph node ratio (LNR: number of metastatic nodes/total number of nodes harvested) has been previously suggested as a quality and prognostic marker. Here, we assess the impact of prior irradiation on the lymph node yield (LNY) as well as the role of LNR in both selective and modified radical neck dissection. We found that previous irradiation to the neck leads to a reduced LNY; there is no change in LNR. LNR has a prognostic impact in modified radical neck dissection but not in selective neck dissection. ABSTRACT: Background: Lymph node metastases are associated with poor prognosis in head and neck squamous cell carcinoma (HNSCC). Neck dissection (ND) is often performed prior to or after (chemo)radiation (CRT) and is an integral part of HNSCC treatment strategies. The impact of CRT delivered prior to ND on lymph node yield (LNY) and lymph node ratio (LNR) has not been comprehensively investigated. Material and methods: A retrospective cohort study was conducted from January 2014 to 30 June 2019 at the University Hospital of Bern, Switzerland. We included 252 patients with primary HNSCC who underwent NDs either before or after CRT. LNY and LNR were compared in patients undergoing ND prior to or after CRT. A total of 137 and 115 patients underwent modified radical ND (levels I to V) and selective ND, respectively. The impact of several features on survival and disease control was assessed. Results: Of the included patients, 170 were male and 82 were females. There were 141 primaries from the oral cavity, 55 from the oropharynx, and 28 from the larynx. ND specimens showed a pN0 stage in 105 patients and pN+ in 147. LNY, but LNR was not significantly higher in patients undergoing upfront ND than in those after CRT (median: 38 vs. 22, p < 0.0001). Cox hazard ratio regression showed that an LNR ≥ 6.5% correlated with poor overall (HR 2.42, CI 1.12-4.89, p = 0.014) and disease-free survival (HR 3.416, CI 1.54-754, p = 0.003) in MRND. Conclusion: ND after CRT leads to significantly reduced LNY. An LNR ≥6.5% is an independent risk factor for decreased overall, disease-free, and distant metastasis-free survival for MRND.