Objective: To explore the relationship of dose-volume histogram (DVH) parameters and computed tomography grading of radiation-induced lung injury in patients with non-small cell lung cancer (NSCLC) treated by three-dimensional conformal radiotherapy (3D-CRT).

Methods: One hundred sixty-nine patients with stage I approximately III NSCLC, treated by 3D-CRT and followed by CT scan for more than six months after 3D-CRT, were divided into grade 0 to grade 4 based on the appearance of radiation-induced lung injury on CT image defined jointly by radiotherapist and radiologist. The patients were divided into CT positive group (grade 2 to grade 4) and CT negative group (grade 0 to grade 1), then the treatment planning shown to the patients were reviewed to compare and analyze the relationship of CT grading of radiation-induced lung injury and the DVH parameter selected.

Results: Regardless of whole lung or tumor-bearing lung, there was a statistically significant difference in normal tissue complication probability (NTCP) between the patients grouped with different CT grading of radiation-induced lung injury, and the mean of NTCP increased along with upgrade of CT grading. There was a statistically significant difference of mean lung dose (MLD) regardless of whole lung or tumor-bearing lung between the patients grouped with different CT grading of radiation-induced lung injury, and MLD increased along with upgrade of CT grading. There was a statistically significant difference of the volume received equal or more than 20 Gy (V(20)), 30 Gy (V(30)), 40 Gy (V(40)) of whole lung and tumor-bearing lung between the patients grouped with different CT grading of radiation-induced lung injury, and V(20), V(30), V(40) increased along with upgrade of CT grading. There were not statistically significant differences of the DVH parameters of the contralateral lung in the patients of different groups based on the CT grading. On statistical analysis, the DVH parameters of whole lung and tumor-bearing lung closely correlated with CT grading of radiation-induced injury of the tumor-bearing lung, and there was a relatively strongest relationship between NTCP and CT grading of the tumor-bearing lung (eta = 0.522).

Conclusion: DVH parameters such NTCP, MLD, V(20), V(30), and V(40) are statistically correlated closely with CT grading of radiation-induced lung injury after radiotherapy for the patients with NSCLC treated by 3D-CRT. Therefore the parameters can be selected as the reference for evaluation after 3D-CRT for patients with NSCLC.