Radiological Evolution of Patients with COVID-19 Pneumonia Treated with Low-Dose Radiotherapy

Background: The main objective of this work is to describe the findings and radiological evolution on chest CT of 27 patients with COVID-19 pneumonia after being treated with LD-RT in a prospective study. We also evaluated the interobserver agreement in assessing the extent of lung involvement. Patients and Methods: 3 CTs were compared: day of treatment, one week later, and at 4-7 months. In each CT the following radiological findings were evaluated in each lobe: extension score (0: none, 0%; 1: minimal, 1-5%; 2: mild, 5-25%, 3: mild-moderate, 26-50%; 4: moderate, 51-75%; 5: severe, 76-100%), GGO, consolidation, crazy-paving pat-tern, subpleural lines, parenchymal bands, and pulmonary fibrosis. Results: A statistically significant decrease in the number of affected lobes with consolidations and GGO was found between the second and third CT (p=0.023 and p=0.003, respectively) and between the first and third CT (p=0.012 and p=0.006). No significant changes were identified regarding the presence of fibrosis. There was a significant decrease of the extension score when comparing the three studies (1st vs 2nd p=0.029, 2nd vs 3rd p<0.001, and 1st vs 3rd p<0.001). A very good concordance was found in the evaluation of the extension score and the presence of consolidations, there was a moderate agreement when assessing the fibrosis and only a mild agreement on the GGO. Conclusions: Our study suggests that patients with COVID-19 pneumonia treated with LD-RT show radiological improvement of consolidations and GGO on long-term follow-up chest CT, with no significant increase in pulmonary fibrosis identified.