The Double-Edge Role of the Addition of Adjuvant Chemotherapy to Concurrent Chemoradiotherapy in the Treatment of Nasopharyngeal Carcinoma

PURPOSE: To construct a prognostic index (PI) for overall survival (OS) to stratify nasopharyngeal carcinoma (NPC) into high-risk and low-risk groups. We also applied the model to investigate the role of the addition of adjuvant chemotherapy (AC) to concurrent chemoradiotherapy (CCRT) regimens for the treatment of NPC. METHODS: A prognostic model was established based on a retrospective study of 362 patients from January 2008 to June 2011. The discriminative and calibration abilities of the model were evaluated by Harrell’s concordance index (C-index), and calibration curves. Bootstrapping was used to perform for internal validation. External validation was conducted using 324 patients diagnosed with NPC from July 2011 to December 2012 at the same institution. Survival analyses were performed between CCRT-AC and CCRT alone groups for the high-risk and low-risk groups. RESULTS: The primary PI comprised covariates that were associated with OS in the training cohort, including T stage, N stage, age, and plasma alkaline phosphatase (ALP). Internal and external validation showed that the discrimination of the PI for OS was significantly better than that of the 8th edition AJCC staging system. Discretization by using a fixed PI score cut-off of 407.96 determined from the training data set yielded high- and low-risk subgroups with distinct OS outcomes in the validation cohort. Adjuvant chemotherapy improved OS in high-risk patients (HR 0.620, 95% CI 0.408 to 0.941; P = 0.023) but increased the risk of distant metastasis (HR, 4.222, 95% CI, 0.959 to 18.585; P = 0.038) in low-risk patients. CONCLUSION: The proposed prognostic model achieved good prediction and calibration of OS for patients with NPC. The addition of adjuvant chemotherapy might be a double-edged sword, bringing survival benefit to high-risk patients but greater risk of distant metastasis to low-risk patients.