Validation and Comparison of the 7(th) Edition of the American Joint Committee on Cancer Staging System and Other Prognostic Models to Predict Relapse-Free Survival in Asian Patients with Parotid Cancer

Purpose: Parotid cancer is a rare malignancy characterized by a heterogeneous histologic subtype and distinct biologic behavior. The present study aimed to externally validate and compare the performances of the American Joint Committee on Cancer (AJCC) staging system (7(th )Edition), Carrillo score, and Vander Poorten score in the prediction of tumor relapse probability in a large cohort of Asian parotid cancer patients. Methods: In total, 261 patients who underwent primary surgery for localized parotid cancer between 2002 and 2014 at the four affiliated hospitals of Chang Gung Memorial Hospital were identified. All patients were categorized into different prognostic groups defined by these three models for the comparison of associated relapse-free survival (RFS) rates. Results: The 5-year overall survival, cancer-specific survival, and RFS rates were 82.9%, 86.2%, and 77.5%, respectively. All three models were significantly powerful in discriminating between the tumors of patients in the lowest and highest risk groups. The c-statistic for predicting the 5-year RFS was 0.74 for the AJCC staging, 0.74 for the Vander Poorten score, and 0.62 for the Carrillo score. The AJCC staging and Vander Poorten score gave significantly high c-statistic values compared to the Carrillo score. Conclusion: Our data validated that all three models are significantly powerful in discriminating tumor relapse between patients in lowest and highest risk groups. The AJCC system and Vander Poorten score proved superior to the Carrillo score, and showed similar performances in discriminating between the 5-year RFS probabilities of low and high-risk Asian parotid cancer patients.