Risk stratification model based on estimated dose of radiation to immune cells and radiotherapy-related nadir lymphocyte count for predicting the efficacy of consolidation immunotherapy in stage III non-small cell lung cancer.

PURPOSE: This study aimed to evaluate the prognostic value of the estimated dose of radiation to immune cells (EDRIC) and the radiotherapy-related nadir lymphocyte count (RT-NLC), and to establish a risk stratification model for predicting outcomes in patients with unresectable stage III non-small cell lung cancer (NSCLC) treated with definitive chemoradiotherapy (CRT) and immunotherapy.

MATERIALS AND

METHODS

We retrospectively analyzed 136 patients treated between May 2019 and November 2023. EDRIC and RT-NLC were dichotomized at median values. Survival analysis was performed using Kaplan-Meier and Cox regression. High-risk patients were defined as having EDRIC ≥ 6.75 Gy and RT-NLC < 0.54×109/L.

RESULTS

EDRIC inversely correlated with RT-NLC (r = -0.38, P < 0.001). Lower EDRIC was associated with significantly improved median overall survival (OS: 49.7 vs. 38.1 months, P = 0.015), progression-free survival (PFS: 29.7 vs. 17.3 months, P = 0.006), locoregional relapse-free survival (LRFS: 32.4 vs. 19.8 months, P = 0.004), and distant metastasis-free survival (DMFS: 44.8 vs. 24.0 months, P = 0.001). On multivariable analysis, low EDRIC independently predicted improved OS (HR = 0.51), PFS (HR = 0.56), LRFS (HR = 0.53), and DMFS (HR = 0.42). High RT-NLC group was significantly prolonged median DMFS (44.8 vs 26.8 months, P = 0.012). High-risk patients demonstrated inferior survival (P < 0.05) but derived significant benefit from consolidation immunotherapy, with improved OS (HR = 0.37, P = 0.041), PFS (HR = 0.44, P = 0.034), and DMFS (HR = 0.33, P = 0.011).

CONCLUSIONS

EDRIC and RT-NLC are significant prognostic biomarkers in unresectable stage III NSCLC. A risk model integrating these parameters effectively identifies high-risk patients who obtain substantial survival benefit, particularly in distant metastasis control, from consolidation immunotherapy, supporting personalized treatment strategies. Prospective validation is warranted.