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Otolaryngology–Head and Neck Surgery 154(1)

histopathologies within parotid cancers makes it challenging to plan appropriate therapy from scarce data. Regional metastatic disease has long been known to have prognostic and therapeu tic implications. This study provides a descriptive analysis for each studied histopathologic entity, identifying predictors of nodal disease and showing its effect on survival. We identify specific predictive factors to guide the clinician in addressing regional nodes. Previous studies on this subject were typically small, single-institution case series or pooled all salivary sites for statistical analysis. 4-8 This is problematic, since the rate of metastasis and behaviors are different among primary salivary sites (ie, parotid, submandibular, sublingual, and minor sali vary glands). 7 Occult nodal data for individual histologies are more rare and depend on extent and prevalence of nodal sam pling and/or neck dissection. In this study of 22,654 patients with parotid cancer, we found that for all histopathologies combined, presence of regional metastasis causes a significant 39% decrease in 5 year OS (40% vs 79% without neck disease). With histolo gies combined, we found nodal disease in a quarter of cases (24.4%), which compares favorably to literature estimates (15%-38%). 6,19,21,28,29 However, because we included only patients with pathologic lymph node evaluation, the real incidence may be even lower, given this selection bias. Prior studies also used grade as a determinant of neck treat ment and negative prognostic factor, with high-grade tumors having higher regional metastasis and poorer survival. In this study, high-grade tumors had a 5-year OS of 44% (vs 85% for low grade) and a 50.9% incidence of neck metasta sis (vs 9.3% in low-grade tumors). Finally, stage is shown to have prognostic implications. When all histologies were grouped, 5-year OS for stage I (81%) was significantly better than II (72%), III (58%), and IV (28%). A number of important clinical and histologic variables have been described for predicting poor outcomes and clini cal and occult nodal disease. For nodal disease, predictors include histologic type, grade, presence of facial nerve dys function, tumor size . 5 cm, age . 54 years, extraglandular spread, and perilymphatic spread. 13,20,21 Although we found age, sex, race, grade, and T stage significant predictors for certain histopathologies in univariate analysis, only age, high-grade tumors, male sex, and high T stage remained sig nificant predictors in multivariate analysis for select histolo gies. Specifically, age . 62 years was a significant predictor only in mucoepidermoid carcinoma, and male sex was pre dictive only in adenocarcinoma NOS. Curiously, despite its OR of 1.8 in univariate analysis, old age showed a ‘‘protec tive effect’’ in multivariate analysis for mucoepidermoid carcinoma (OR, 0.697; 95% CI, 0.555-0.872; P = .002). It is not immediately clear why this is the case, suggesting that there may be other variables not being controlled for. 13,20 Race was not predictive for any histology in our study. More consistently predictive were high T stage and high grade disease. In a similar thread, Bhattacharyya and Fried found that only tumors approaching sizes of 5 cm were independently predictive. 4 While T4 was most predictive in our data, T2 and T3 remained significant predictors for

Table 5. Five-Year Overall Survival by Stage.

Histology: Stage

5-y Overall Survival, %

Mucoepidermoid carcinoma I

84 72 58 26 89 87 70 40 66 52 41 18 86 77 84 47 91 69 69 34 82 61 55 28 82 71 69 40 81 81 69 43 81 72 58 28

II

III IV

Acinar cell carcinoma I

II

III IV

Adenocarcinoma, not otherwise specified I

II

III IV

Adenoid cystic carcinoma I

II

III IV

Carcinoma ex-pleomorphic adenoma I

II

III IV

Salivary ductal carcinoma I

II

III IV

Epithelial-myoepithelial carcinoma I

II

III IV

Basal cell adenocarcinoma I

II

III IV

Total I

II

III IV

Discussion

Parotid cancers represent approximately 3% of all head and neck cancers, 3 making it a difficult primary site for prospective studies or studying therapeutic outcomes from single institu tions. 4,5,7,8,24-27 Additionally, the enormous variety of