Optimal dose-volume histogram thresholds for radiation pneumonitis prevention in lung cancer patients receiving immunotherapy.

Objectives: To evaluate the incidence of symptomatic radiation pneumonitis (RP) in lung cancer patients receiving immunotherapy and radiotherapy.

Materials and methods: We retrospectively analyzed 389 lung cancer patients who underwent thoracic radiotherapy with/without immunotherapy at the Third Xiangya Hospital (January 2015-September 2024). Propensity score matching (PSM) was employed to compare RP incidence. Univariate, multivariate, and stepwise regression analyses were conducted to identify predictors of grade ≥ 2 RP.

Results: Symptomatic RP occurred in 30.33% (118/389) and 7.46% (29/389) of patients for grades ≥ 2 and ≥ 3, respectively. Patients receiving concurrent immunotherapy-radiotherapy demonstrated a significantly lower incidence of grade ≥ 2 RP compared to other treatment groups (p < 0.05). Multivariable analysis revealed no significant association between immunotherapy administration and RP risk. Lung V20 (≤ 20% vs. > 20%) emerged as a critical predictor: grade ≥ 2 RP incidence was 4.05-8.73% with V20 ≤ 20%, versus 53.8-65.5% when V20 exceeded 20%.

Conclusions: Immunotherapy did not raise the risk of grade ≥ 2 RP. Maintaining lung V20 ≤ 20% may serve as an optimal dosimetric threshold for RP prevention in patients undergoing combined-modality therapy.

Clinical trial number: Not applicable.