2188 - Incidence, Risk Factors and CT Characteristics of Radiation Recall Pneumonitis Induced by COVID-19 Infection in Lung Cancer

W. Yun¹, X. Zhai², K. Zhao³, X. Yin³, and X. Meng³; ¹Shandong Cancer Hospital and Institute,Shandong First Medical University and Shandong Academy of Medical Sciences, jinan, shandong, China, ²Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, ³Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China

Purpose/Objective(s): Radiation recall pneumonitis (RRP) is unpredictable and usually caused by antitumor drugs, resulting in pulmonary toxic damage in previously irradiated lung tissue areas. Recently, COVID-19 infection was found to cause RRP, however, its actual incidence rate and potential risk factors remain unclear. Materials/

Methods: We recruited two cohorts of patients between November 2022 and February 2023: those infected with COVID-19 and treated with radiotherapy and those infected with COVID-19 without radiotherapy. We defined RRP as lung CT changes occurring at the previous irradiation site at least six months after the completion of radiotherapy. The clinical and dosimetric data of patients were analyzed to identify potential risk factors for RRP.
Results: We eventually enrolled 140 patients who had been infected with COVID-19 and had completed radiotherapy for at least six months, of whom 62 (44.2%) had RRP. This rate of pneumonitis is much higher than in patients infected with COVID-19 but not treated with radiotherapy (24.8%). In the RRP population, the incidence of grade=2 pneumonitis was 45.1%. No radiotherapy dosimetric risk factors were significantly associated with the development of RRP. But the T stage in naïve (P=.034) and interval between radiotherapy and COVID-19 infection(P=.001) were related to the occurrence of RRP.
Conclusion: Our study shows that the incidence of RRP caused by COVID-19 is higher than expected (44.2%). We identified no dosimetric risk factors for RRP. However, RRP was associated with T stage in naïve and the time interval between the end of radiotherapy and COVID-19 infection.