Eosinophil dynamics during chemo-radiotherapy correlate to clinical outcome in stage Ⅱ-Ⅳa nasopharyngeal carcinoma patients: Results from a large cohort study

Background and purpose We investigated the dynamics of eosinophil depletion during definitive concurrent chemo-radiotherapy (CCRT) and their association with the prognosis of stage Ⅱ-Ⅳa nasopharyngeal carcinoma (NPC) patients. Materials and methods Fuzzy C-means algorithm (FCMA) assessed longitudinal trends in circulating eosinophil counts (CECs) of 1225 patients throughout the period of radical radiotherapy. The prognostic impact on patients' survival was evaluated with Kaplan-Meier analysis and Cox proportional risk model was used to determine the hazard ratio for adverse prognostic effects in grades of eosinophil depletion. The interactive effect of pre-treatment CECs and CCRT on outcomes was evaluated using HRs within the framework of Cox regression models. Results Three grades of eosinophil depletion, as defined by the interaction between dynamic types of CECs in the period of treatment and the value of CECs at the termination of treatment, significantly stratified the poor prognosis in terms of progression-free survival (PFS), overall survival (OS), and distant metastasis-free survival (DMFS) [1.57-fold (P = 0.001), 1.69-fold (P = 0.007), and 1.51-fold (P = 0.019) for G1, 2.4-fold (P < 0.001), 2.76-fold (P < 0.001), and 2.31-fold (P < 0.001) for G2, as compared with G0]. Furthermore, high levels of pre-treatment CECs acted as the strongest protective factor against severe depletion grade (G0 vs. G2, HR = 0.20, P = 0.005; G1 vs. G2, HR = 0.14, P < 0.001). However, compared with radiotherapy alone, the benefit from CCRT was attenuated in patients with high pre-treatment CECs. Conclusions CECs reduction after treatment in patients with NPC may be helpful in the clinical setting to aid in assessing the prognosis for standard treatment of NPC.