Low-dose radiation therapy for COVID-19

Background. Radiation therapy is one of the most effective treatments in patients with malignant neoplasms, it also plays an important role in the treatment of non-oncological di­seases. The coronavirus disease 2019 (COVID-19) pandemic has prompted a review of the long-forgotten idea of using low-dose radiation therapy (LDRT) in patients with lobar and interstitial pneumonia. Historically, from 1905 to the mid-1940s, LDRT was used to treat pneumonia, and evidence suggests that it might improve survival and provide rapid relief of respiratory symptoms. The purpose was to summarize current information about ­using low-dose radiation therapy in the treatment of patients with ­COVID-19. Materials and methods. A selection of publications was carried out, which covered information on the possibilities of using low-dose radiation therapy in the treatment of patients with COVID-19. At the first stage, a search was conducted for lite­rary sources using the keywords: COVID-19, low-dose radiation therapy. At the second stage, summaries of articles were studied and publications that did not meet the research criteria were excluded. At the third stage, the full texts of the selected articles were studied for compliance with the criteria for inclusion in the reference list and research relevance. Results. As of August 1, 2023, according to ClinicalTrials.gov, among 9,244 clinical trials associated with COVID-19, sixteen are currently being conduc­ted. They examine the effectiveness of LDRT in the treatment of patients with COVID-19 and already involve 1,038 patients. The largest number of studies is conducted in European countries. It has been shown that LDRT selectively attenuates oxidative stress to an inflammatory stimulus and inhibits the nitric oxide production pathway. This may contribute to its anti-inflammatory and vascular effects. At the same time, heme oxygenase 1 and other antioxidants are induced, they are mediated by Nrf2, which is the main regulator of endogenous antioxidant, anti-stress, analgesic reactions, and is also closely related to nicotinamide adenine dinucleotide phosphate and the metabolic pathway of pentose phosphate. Nrf2 may be critical for pain relief associated with edema formation and possibly plays a major role in the effects of LDRT, whereas direct functional effects of low-dose radiation on the autonomic nervous system and nociception are likely to be smaller. Conclusions. From 1905 to 1946, researchers published the results of more than 15 clinical studies on the effectiveness of radiotherapy for inflammatory lung diseases, which included more than 850 patients and demonstrated the high therapeutic effectiveness of radiation therapy in the indicated pathology. Today, there are 16 ongoing clinical trials in the world devoted to the study of LDRT effectiveness in the treatment of patients with COVID-19, in which 1,038 patients have already been involved. The risk of radiation-induced lung and breast cancer in a 25-year-old woman exposed to 1 Gy whole chest radiation may be as high as 5.9 and 5.5 %, respectively.