Incidence, Risk factors, and CT Characteristics of Radiation Recall Pneumonitis Induced by COVID‐19 Infection in Lung Cancer

Objective Radiation recall pneumonitis (RRP) is a localized inflammatory reaction occurring in previously irradiated lung regions, typically triggered by certain anticancer agents. In clinical settings, we have observed that COVID‐19 infection may also act as a precipitating factor for RRP. However, its true incidence and possible risk factors remain poorly defined. Methods Lung cancer patients who received radiotherapy and were diagnosed with COVID‐19 between November 2022 and February 2023 were included. RRP was defined as pulmonary changes limited to the previously irradiated regions, occurring at least 6 months after radiotherapy. Patients medical records and radiation dose distribution data were analyzed to identify potential contributing factors to RRP. Results The study included 140 patients who underwent thoracic radiotherapy with a minimum six‐month interval before COVID‐19 diagnosis. Among these, 62 patients (44.2%) developed RRP, and 45% of these experienced grade ≥ 2 pneumonitis. No radiotherapy dose‐related factors were significantly associated with RRP. However, statistical analysis showed that RRP incidence was significantly associated with baseline T‐stage ( P = 0.034) and the time interval from radiotherapy completion to COVID‐19 infection ( P < 0.001). Conclusions A 44.2% incidence of COVID‐19‐related RRP was identified, which is notably higher than previously reported. While radiotherapy dosimetry did not correlate with RRP risk, baseline T‐stage and timing of COVID‐19 infection after radiotherapy were significantly associated with its occurrence.