Radiation-induced lung injury patterns and the misdiagnosis after SBRT of lung cancer

•Radiation-induced lung injury after SBRT was various and complicated.•The complicated injury patterns may induce misdiagnosis in clinical practice.•Our data showed that 24.5% patients were misdiagnosed after receiving SBRT.•Based on Koening’s classification, mass-like pattern was misdiagnosed the most.•A nomogram was developed and showed a predictive value in clinical practice. To analyze radiation-induced lung injury (RIL) after stereotactic body radiotherapy (SBRT) of lung cancer and the subsequent clinical problems. 106 lung cancer patients treated with SBRT were included, their computed tomography (CT) scans were reviewed. Late injury pattern was classified by Koening’s, radiologist’ diagnosis reports for RIL was reviewed. Logistic regression was used to analyze the predictive model of injury pattern, which was also validated by ROC curve. Radiographic late injury within at least 6 months after SBRT was concluded. The majority of late RIL was mass-like pattern, not the modified conventional pattern. 36.8% patients showed acute injury, which trend to occur late lung injury earlier than patients who were not found acute injury (p = 0.0185). 24.5% RIL cases were misdiagnosed to tumor progression by radiologists. Most misdiagnosis occurred among mass-like pattern. Per fraction dose (p