Correlation Between Lower Lobe Dose Parameters and Radiation Pneumonitis in Definitive Radiation Therapy for Non‐Small Cell Lung Cancer
Sachiko Miura, Nobuhide Wakai, Shigeto Hontsu, Masahide Ota, Kaori Yamaki, Tetsuro Tamamoto, Masayuki Takeda, Fumiaki IsohashiABSTRACT
Background
This study examined whether lobar‐specific dose‐volume histogram (DVH) parameters add predictive information for radiation pneumonitis (RP) beyond conventional whole‐lung parameters in patients with non‐small cell lung cancer (NSCLC) undergoing definitive radiotherapy.
Methods
We retrospectively analyzed 145 NSCLC patients treated between 2018 and 2023. Conventional whole‐lung parameters, including V5%, V20%, and mean lung dose (MLD), lobar‐specific parameters, including Low V20% (percentage of the bilateral lower lobes receiving ≥ 20 Gy), and clinical parameters were analyzed. The predictive performance of each parameter for Grade ≥ 2 RP was evaluated using receiver operating characteristic curve analysis. Associations with Grade ≥ 2 RP were assessed by Gray test and Fine‐Gray competing risks regression.
Results
Grade ≥ 2 RP had an incidence of 41% (60/145) and showed significant associations with V20% ( p = 0.005), MLD ( p = 0.025), Low V5% ( p = 0.006), and Low V20% ( p = 0.003). In multivariate analysis, a high Brinkman Index (BI) (HR = 2.10, 95% CI: 1.27–3.48, p = 0.004) and high Low V20% (HR = 2.31, 95% CI: 1.12–4.74, p = 0.023) were independent predictors for Grade ≥ 2 RP. The correlation between V20% and Low V20% was moderate ( r = 0.505), with minimal multicollinearity (variance inflation factor 1.34).
Conclusion
Low V20% was independently associated with Grade ≥ 2 RP and may provide complementary information to conventional whole‐lung DVH parameters and BI. This simple lobar‐specific parameter may help refine pretreatment RP risk stratification, although external validation is required before its incorporation into individualized planning constraints.