Management of Clinically Node-Negative Salivary Gland Cancer: Observation, Neck Dissection, or Neck Irradiation?

Introduction: Salivary gland malignancies are heterogeneous tumors with highly variable outcomes. Elective neck management options include observation, neck dissection (ND), and neck irradiation (NI). We sought to compare outcomes of cN0 salivary gland cancer by elective neck management.

Methods: An IRB-approved registry was queried for cN0 salivary gland cancers and categorized based on neck management into observation, ND, NI, and ND + NI groups. cN0 included no evidence of clinical or radiographic metastatic lymphadenopathy.

Results: A total of 445 patients were included with 203 in observation, 83 ND, 71 NI, and 88 ND + NI. Median follow-up was 60.8 months (range 0.4-258). There were 47% clinical T1 tumors, 29% T2, and 12% of each T3 and T4. Exactly 90% were cN0 and 10% with borderline lymph node(s). The major salivary gland was the most common site (74%) and the most common histologies included 28% mucoepidermoid and 20% adenoid cystic. Risk factors associated with regional recurrence include age, borderline lymph node features, pathologic T and N stage, poorly differentiated, positive margin, lymphovascular space invasion, and extranodal extension (all p < 0.05). There was no significant difference in local (9.9%-16.7%, p = 0.6) or regional (3.9%-9.4%, p = 0.76) recurrence between all four groups. Five-year distant recurrence was significantly different at 7% for observation, 16% in ND, 25% in NI, and 37% in ND + NI (p < 0.001). Ten-year OS estimates were 78% for observation, 66% for ND, 69% for NI, and 52% in ND + NI (p < 0.001).

Conclusion: For patients with cN0 salivary gland cancer, ND and NI yield similar regional control in appropriately selected patients. In high-risk patients with several adverse risk features ND + NI results in favorable regional control but distant metastasis is a driving factor affecting overall survival.