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 ( 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.