Impact of radiation dose to the immune cells in stage IV non-small cell lung cancer in the era of immunotherapy.

person Junyi He Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong University , Jinan, China, Jinan, No, China info_outline Junyi He, Yingxin Liu, Butuo Li, Jinming Yu, Linlin Wang

Authors person Junyi He Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong University , Jinan, China, Jinan, No, China info_outline Junyi He, Yingxin Liu, Butuo Li, Jinming Yu, Linlin Wang Organizations Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong University , Jinan, China, Jinan, No, China, Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong University , Jinan, China, China, China, Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Science, Jinan, China, Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Science, Jinan, China, Jinan, Shandong, China Abstract Disclosures Research Funding No funding sources reported Background: Thoracic radiotherapy now is widely accepted in advanced lung cancer. It is not only been used as palliative therapy but also been involved in Systemic treatments in advanced lung cancer, especially in immune era. However, radiotherapy impairs immune system which can be evaluated by estimated dose of radiation to immune cells (EDRIC). Here, we sought to examine the prognostic impact of the EDRIC in advanced NSCLC in the context of immunotherapy, and to identify the factors influencing EDRIC in this population. Methods: We retrospectively enrolled patients with stage IV NSCLC who had received first-line immunotherapy and thoracic radiation therapy. EDRIC is a specific formulation using a model developed by Jin et al and improved by Ladbury et al, calculated using radiation fraction, mean lung dose (MLD), mean heart dose (MHD), and mean body dose (MBD). Spearman’s rank correlation was used to assess the correlation between variables.Associations between EDRIC [analyzed continuously and categorically (<5.7Gy vs ≥5.7Gy)] and overall survival (OS) and progression-free survival (PFS) were evaluated by Kaplan-Meier and Cox proportional methods. Results: We conducted a retrospectively analysis of 152 patients with stage IV NSCLC patients. GTV (r = 0.2023, p = 0.0137), PTV (r = 0.4139, p < 0.0001) and N (r = 0.1897, p = 0.0193) stage showed a positive correlation with EDRIC. Negative correlations of lymphocyte nadir with EDRIC (r = -0.3172, p < 0.0001), during/pre lymphocyte nadir with EDRIC (r = -0.2102, p = 0.0093), during/post lymphocyte nadir with EDRIC (r = -0.2750, p = 0.0006) were found. Median PFS was shorter among the EDRIC ≥5.7Gy group (10.2months vs 18.6months; p < 0.0001). Median OS was also shorter among the EDRIC ≥5.7Gy group (19.8 months vs 30.2months; p = 0.024). For ORR (38% vs 46%; p = 0.413) and DCR (84% vs 92%; p = 0.304), there was no statistical significance between EDRIC≥5.7Gy and EDRIC < 5.7Gy. Analyzed as a continuous variable, EDRIC was the only factor associated with worse PFS (HR = 1.001, p = 0.018) and OS (HR = 1.002, p = 0.001) in multivariate analysis. Conclusions: In the era of immunotherapy, EDRIC is an independent predictor for PFS and OS in advanced NSCLC, warranting investigation into techniques to optimize radiation dose to the immune compartment.