The Risk And Predictors For Severe Radiation Pneumonitis In Lung Cancer Patients Treated With Thoracic Reirradiation

Purpose: To determine risk and predictors for severe radiation pneumonitis(RP)in patients receiving thoracic reirradiation(re-RT).Methods and Materials: 67 patients with lung cancer received thoracic re-RT for recurrent or metastatic disease.Three-dimensional conformal radiotherapy(3D-CRT)/intensity modulated radiotherapy(IMRT)was used for 60 patients,and stereotactic body radiation therapy(SBRT)was used in 7 patients.Severe(grade≥3)RP was graded according to Common Terminology Criteria for Adverse Events version 4.0.Results: 18 patients(26.9%)developed grade≥3 RP(17 of grade 3,and 1 of grade4).In univariate analyses,V5 and mean lung dose(MLD)of initial RT or re-RT plans,V5 and V20 of composite plans,and the overlap between V5 of initial RT and V5 of re-RT plans/V5 of re-RT plans(overlap-V5/re-V5)were significantly associated with grade≥3 RP(P<0.05 for each comparison).Multivariate analysis revealed that MLD of the initial RT plans(initial-MLD)(P=0.013),V5 of the composite plans(composite-V5)(P=0.023),and overlap-V5/re-V5(P=0.041)were independent predictors for grade≥3 RP.Linear-by-linear association testing revealed a significant correlation between location of re-RT(in-field/out-of-field)and overlap-V5/re-V5(0.8-1/0-0.8)(P<0.001).Conclusions: The risk of grade≥3 RP was relatively common for patients receiving re-thoracic RT,and could be predicted by initial-MLD,composite-V5,and overlap-V5/re-V5.