Objective To compare the efficacy of dosimetric parameters defined by different lung volume methods in predicting radiation pneumonitis (RP) in patients with non-small cell lung cancer after radiotherapy.

Methods A total of 92 patients with non-small cell lung cancer who received intensity-modulated radiotherapy were selected as study objects. Total lung volume, planned target volume (PTV) and planned gross tumor target volume (PGTV) were recorded by CT scan. Dosimetric parameters including volume percentage of normal lung relative volume receiving greater than 5 Gy (V₅), volume percentage of normal lung relative volume receiving greater than 20 Gy (V₂₀) and mean lung dose (MLD) were defined by three lung volume methods (total lung volume, PTV and PGTV). The primary endpoint was symptomatic RP. The correlations of symptomatic RP with dose parameters(V₅, V₂₀ and MLD) were analyzed by Logistic regression, and the performance of MLD in predicting symptomatic RP was assessed using the area under the receiver operating characteristic curve (AUC).

Results Of 92 patients, 13 developed acute symptomatic RP within 3 months after treatment. There were significant differences in V₅, V₂₀ and MLD defined by PTV in symptomatic RP compared with non-symptomatic RP patients (P < 0.05). Logistic regression analysis showed that MLD defined by PTV method and PGTV method was associated with the incidence of symptomatic RP (P < 0.05). In predicting symptomatic RP, MLD defined by PTV had the highest AUC value (0.798), which was significantly higher than 0.699 by PGTV and 0.605 by whole lung volume (P < 0.05).

Conclusion Dosimetric parameters defined by PTV have high value in predicting symptomatic RP in lung cancer patients undergoing intensity-modulated radiotherapy.