The Impact of Radiation Dose to Immune Cells in Stage IV Non-Small Cell Lung Cancer in the Era of Immunotherapy.

Purpose: Thoracic radiotherapy (RT) is now widely used in the treatment of advanced non-small cell lung cancer (NSCLC) as palliative, consolidative or radical therapy. However, RT adversely impacts the immune system, which can be evaluated by calculating the estimated dose of radiation to immune cells (EDRIC). We evaluated the prognostic impact of the EDRIC in patients with advanced NSCLC who received immunotherapy and thoracic RT.

Methods: We retrospectively enrolled 152 stage IV NSCLC patients who had received first-line immunotherapy and thoracic RT. EDRIC was a model developed by Jin et al., calculated using the number of radiotherapy fractions, mean lung dose, mean heart dose, and mean body dose. Spearman's rank correlation was used to assess the correlations between variables. The relationships of EDRIC (≥5.7 Gy vs. <5.7 Gy) with survival were assessed using Kaplan-Meier and Cox proportional hazard models.

Results: The median PFS and OS were shorter in the EDRIC ≥ 5.7 Gy group (PFS: 10.2 months vs. 18.6 months, P < .0001; OS: 19.8 months vs. 30.2 months, P = .024). In the multivariate model, higher EDRIC was associated with worse PFS (HR = 2.791, P < .0001) and OS (HR = 1.823, P = .028). Additionally, bone metastasis was associated with worse OS (HR = 1.751, P = .022).

Conclusion: EDRIC was an independent predictor for PFS and OS in advanced NSCLC patients receiving immunotherapy and RT. These observations necessitate further exploration into techniques to optimize radiation exposure to the immune system in cancer treatment.