Purpose: To identify significant prognostic factors that can be used in clinical decision-making with regard to parotid cancer, which is characterized by a complex and diverse group of tumors with variable outcomes.
Methods and materials: A historical cohort of 184 patients with parotid-gland malignancy, who had been registered in the Province of Manitoba from 1970 to 2003, was examined. Survival analysis was performed using Kaplan-Meier curves and a log-rank test for comparing subgroups. The independent effect of factors that predicted survival at the bivariate level was determined using a Cox proportional hazard model.
Results: The mean age at presentation was 62 years. The mean follow-up was 64 months. Absolute and disease-specific survival at 5 years was 41.70% and 57.94%, respectively. Survival for Stages I-IV at 5 years was 85.35%, 76.9%, 56.1%, and 8.4%, respectively (p < 0.0001). Factors with an independent effect on survival (p < 0.05) included age, tumor size, local invasion (Stages T4 vs. T1), and distant metastasis at presentation, tumor differentiation, and treatment. Adjuvant radiotherapy vs. surgery alone reduced the risk of death from disease at 5 years by 50% (hazard ratio [HR], 0.5; 95% confidence interval, 0.228-0.995; p = 0.0486).
Conclusions: Despite the variety of malignant parotid tumors, easily identifiable prognostic indicators such as advanced age, tumor size, local invasion, and tumor differentiation have a significant impact on outcome. Patients with adverse prognostic factors benefit from adjuvant radiotherapy. The threshold for the use of adjuvant radiotherapy in managing parotid malignancy should be low.