Predictors of Nodal Metastasis in Parotid Malignancies: A National Cancer Data Base Study of 22,653 Patients

Objective (1) To identify predictors of nodal disease in parotid malignancies using various clinical and pathologic variables. (2) To examine the effect of nodal disease on overall survival (OS) in parotid cancers Study Design Retrospective database review. Setting National Cancer Data Base (1998-2012). Subjects and Methods We identified all cases of primary parotid malignancies in the United States between 1998 and 2012 in the National Cancer Data Base. Eight histopathologies, constituting >80% of all cases, were examined for nodal metastasis and survival. Results We identified 22,653 cases of primary parotid cancer. Eight major histologies were studied, with mucoepidermoid carcinoma (31%), acinic cell carcinoma (18%), adenocarcinoma (14%), and adenoid cystic carcinoma (9%) being most common. Regional nodal disease incidence was 24.4% overall and varied by histopathology. Salivary ductal carcinoma had the highest incidence of both nodal metastasis and occult lymph node metastasis. Overall, N0 patients lived significantly longer than N+ (5-year OS, 79% vs 40%; P <.001). Low-grade disease had significantly better survival than high-grade (5-year OS, 88% vs 69%; P <.001). Occult nodal disease was found in 10.2% and varied by histopathology. Conclusion Regional lymph node metastasis significantly decreases survival in many parotid malignancies. High-grade cancers had higher incidences of regional disease than did low grade. Adenocarcinoma had the highest mortality when regional disease was present. Incidence of occult disease varied by histology, but incidence was <10% for all low-grade disease. High T stage and grade are significant independent predictors of nodal disease for most histopathologies.