The Prognostic Factors For Radiation Pneumonitis >= Grade 2 In The Definitive Radiation Therapy In Non-Small Cell Lung Cancer Patients.

The purpose of this study is to investigate the prognostic factors for radiation pneumonitis (RP) ≥ grade 2 (the Common Terminology Criteria for Adverse Events version 5.0) in the definitive radiation therapy (DRT) in non-small cell lung cancer (NSCLC) patients. One hundred and forty-eight NSCLC patients who received DRT in our institution from January 2014 to May 2017 were analyzed in detail. Performance status, age, arterial oxygen partial pressure, respiratory function, Brinkman index(BI), the TNM classification (UICC 8th edition), pathology, concurrent administration of chemotherapy, location of the primary tumor, the volume of lung/heart, and dose-volume histogram metrics of lung/heart (mean lung dose, lung V5, 10-50, VS5, VS10-50 and the mean/max dose irradiated to heart) were analyzed to evaluate the relation to grade ≥ 2 RP. Additionally, 3 diagnostic radiologists (a chest radiologist with 32 years of experience, 2 radiologists with 16 and 15 years of experience) evaluated chest computed tomography images of pre-DRT and determined a pulmonary fibrosis score (PFS) without any information of clinical data. PFS was assigned; 0: none, 1: abnormality without honeycombing (ground-glass attenuation, fine reticular opacity, and microcysts), and 2: honeycombing. Univariate logistic regression analysis and Pearson’s χ2 test were used to assess the statistical significance, then factors having a p value of p ≤ 0.05 were assessed by multivariate logistic regression analysis. Median follow-up period was 729 days. Thirty-one patients (20.9%) experienced grade ≥ 2 RP, and 2 patients (1.4%) experienced grade 5 RP. Concurrent chemoradiotherapy was administered to 113 patients. The clinical stage (UICC 8th edition) distribution was IIB (8), IIIA (72), IIIB (48) and IIIC (20). In a univariate analysis, lung V5/V10/V20/V30/V40 (p = 0.013/0.008/0.007/0.010/0.012) and Brinkman index (p = 0.008) were significant prognostic factors, and in Pearson’s χ2 test, high PFS (p < 0.001) was also significantly unfavorable prognostic factors for grade ≥ 2 RP. Additionally, multivariate analysis including BI ≥ 1000, lung V20 ≥ 30%, PFS revealed that only fibrosis scores (p < 0.001) were independent factors for grade ≥ 2 RP. Furthermore, subgroup analysis was carried out. In the group whose PFSs were 0, only lung V5/10/20/30/40 were prognostic factors (p = 0.037, 0.015, 0.013, 0.018, 0.021) for grade ≥ 2 RP. On the other hand, in the group whose PFSs were 1 or 2, lung dose-volume histogram metrics were not prognostic factors, and only BI was a prognostic factor for grade ≥ 2 RP. This is the report on prognostic factors for grade ≥ 2 RP in DRT for NSCLC patients in a single institution. PFS was a significant prognostic factor for grade ≥ 2 RP. Subgroup analysis suggested that dose-volume histogram metrics of lung were significant prognostic factors for grade ≥ 2 RP in patients whose PFSs were 0, but not significant in patients whose PFSs were 1 or 2.