# Predictive Value of the Estimated Dose of Radiation to Immune Cells Versus Conventional Parameters in Elderly Patients With Unresectable Stage III NSCLC: A Two‐Center Real‐World Study

## TL;DR

This study finds that radiation dose to immune cells better predicts survival in elderly lung cancer patients than traditional measures.

## Contribution

EDRIC (estimated dose to immune cells) is shown to be a superior survival predictor compared to conventional dosimetric parameters in elderly NSCLC patients.

## Key findings

- EDRIC ≥ 6.4 Gy independently predicted worse progression-free and overall survival.
- Conventional dosimetric parameters like MLD, MHD, and MBD showed no prognostic significance.
- EDRIC outperformed traditional parameters in predicting 1-, 2-, and 3-year survival rates.

## Abstract

To compare the predictive value of the estimated dose of radiation to immune cells (EDRIC) with conventional dosimetric parameters for survival in elderly patients with stage III unresectable NSCLC after chemoimmunotherapy and radiotherapy.

We conducted a retrospective study of elderly patients (≥ 65 years) treated at two institutions. Patients were stratified by median EDRIC, mean lung dose (MLD), mean heart dose (MHD), and mean body dose (MBD). Survival was analyzed using Kaplan–Meier, Cox regression, and ROC curves.

Baseline characteristics were well‐balanced across dosimetric parameter subgroups (all p > 0.05). The median progression‐free survival (PFS) and overall survival (OS) for the entire cohort were 23.9 months and 46.0 months, respectively. EDRIC ≥ 6.4 Gy was associated with worse PFS (p = 0.019) and OS (p = 0.011), while MLD, MHD, and MBD showed no prognostic significance (all p > 0.05). Multivariate analysis identified EDRIC ≥ 6.4 Gy as an independent predictor of worse PFS (HR = 1.852, p = 0.049) and OS (HR = 2.289, p = 0.048). Age ≥ 70 years was also independently associated with poorer OS (HR = 2.870, p = 0.011). ROC analysis demonstrated superior predictive performance of EDRIC over conventional parameters for 1‐, 2‐, and 3‐year PFS and OS, with particularly outstanding discrimination for 12‐month OS (AUC = 0.93).

EDRIC shows potential in predicting survival for elderly stage III unresectable NSCLC patients, with 6.4 Gy as a potential threshold for personalized radiotherapy optimization. These findings require prospective validation.

In elderly patients with unresectable stage III NSCLC receiving radiotherapy after chemoimmunotherapy, an EDRIC ≥ 6.4 Gy independently predicted poorer survival. EDRIC outperformed conventional dosimetric parameters, suggesting its value in personalizing radiotherapy to improve outcomes.