Elective Neck Treatment for Clinically Node-Negative Salivary Gland Cancer: Observation, Neck Dissection, or Neck Irradiation?

Abstract

<h3>Purpose/Objective(s)</h3> Malignancies of salivary glands are rare and heterogeneous making large comparative studies challenging. Management of the clinically node-negative neck (cN0) varies and the optimal approach is undefined. We present a single institution experience of cN0 salivary gland cancer cases with primary endpoints of local and regional recurrence. We compared four management approaches; observation (None), elective neck dissection (END), elective neck irradiation (ENI), and combined elective neck dissection and neck irradiation (END+ENI). <h3>Materials/Methods</h3> An IRB approved registry of head and neck cancer patients treated at a tertiary care center was queried for diagnoses of cN0 salivary gland cancer. Cases were categorized into observation only, END, ENI, and END+ENI. Tumor and treatment characteristics were compared with Chi-square or Kruskal-Wallis tests. <h3>Results</h3> 445 cases were included in this analysis with median follow up of 60.8 months. The median age of the cohort was 59 years (13-93). The END+ENI group had older patients, the highest proportion of T3 and T4 cases, borderline nodal features, poorly differentiated tumors, perineural invasion (PNI), and lymphovascular space invasion (LVSI) (all p≤0.01). The ENI group had the highest ratio of positive margins (p<0.001). Local and regional recurrence among the 4 groups were not statistically significant. The END+ENI group had the highest incidence of distant metastasis and lowest survival. Univariate analysis revealed a significant effect of clinical T stage (cT), pathological T stage (pT), positive margins, and PNI on local recurrence (all p<0.05). Poor differentiation status, pT, positive margin, PNI, extranodal extension (ENE), and LVSI had significant impact on regional recurrence (all p<0.05). <h3>Conclusion</h3> In this cohort of patients with cN0 neck, local and regional recurrence was similar for END versus ENI. For patients with high-risk factors such as positive margins, poor differentiation, PNI and LVSI, END+ENI results in low local and regional recurrence despite higher risk pathologic features; however, the higher risk of distant recurrence limits survival.