V15(Gy) as a predictor of asymptomatic radiation pneumonitis in patients with lung cancer: A retrospective dosimetric analysis.

Abstract

Purpose: This study aimed to investigate the dose dependency of asymptomatic radiation pneumonitis (aRP) in patients with lung cancer following radiotherapy, focusing on the predictive value of dosimetric parameters.

Methods: This study included 72 patients with primary lung cancer who underwent radiotherapy between January 2019 and June 2022. The patients were divided into an aRP group (n = 30) and a non-RP group (n = 42). The physical dose was converted to an equivalent dose using the Linear-Quadratic (LQ) model, with an α/β value of 3. Three lung structures were defined, and the corresponding dose-volume histogram parameters were collected. The Mann-Whitney U test was used to compare dose parameters between the two groups, and multivariate logistic regression was performed to remove correlations among different parameters. A logistic function and receiver operating characteristic curve were constructed to predict aRP. This study analyzed the impact of different clinical characteristics on the aRP incidence.

Results: The lungs-planning target volume (PTV) V_15(Gy) was ultimately identified as the best predictive parameter. Significant dose-response relationships were observed, with V_15(Gy) achieving an area under the curve of 0.666 ± 0.067 (P = 0.017). The optimal cutoff value for lungs-PTV V_15(Gy) was 21.1%, below which the incidence of aRP decreased significantly. Immunotherapy has been identified as an independent risk factor for aRP.

Conclusion: The occurrence of aRP in patients with lung cancer after radiotherapy has a clear dose dependency, with lungs-PTV, V_15(Gy) being the best dose parameter for prediction, and the optimal cutoff value based on this study was 21.1%.