Low-Dose Radiation Therapy (LDRT) for COVID-19: Benefits or Risks?

Unprecedented Approach for Using Misoprostol Alongside Low-Dose Gamma Radiation to Alleviate Paraquat-Induced Pulmonary Injury in Rats

Background

Abrupt inflammation and alveolar epithelial membrane damage, which may cause the alveolar membrane's malfunction, are related to acute lung injury (ALI). This could eventually lead to pulmonary fibrosis. While lung injury can happen in many ways, the current study will concentrate on the changes in lung pathology mediated by paraquat (PQ). Paraquat, a widely used herbicide, targets lung toxicity through inflammation and oxidative stress, which significantly contribute to lung damage.

Objective

The current research was to ascertain whether low-dose gamma radiation (R) and misoprostol (MP) could lessen the lung inflammatory cascade started by PQ injection in rats.

Methods

The ALI model was induced by I.P. injection of PQ (20 mg/kg once), and then treatment was done by MP and/or R for 14 days, and finally, the biochemical and histological parameters were measured in the lung tissues.

Results

Our data suggest that PQ can promote ALI through TGF-β/smad, Notch, NF-κB, and ET-1 signaling pathways, resulting in EMT. These suggestions were supported by increased levels of TGF-β, inflammatory cytokines, α-SMA, NF-κB, ET-1, CTGF protein, and LPA, whereas PPAR-γ decreased. The aforementioned results have been confirmed by lung histopathology.

Conclusion

We suggest that the pulmonary inflammatory cascade was hindered and all the previously described gauges improved with R and/or MP therapy.

SARS-CoV-2 Spike Protein Induces Oxidative Stress and Senescence in Mouse and Human Lung

BACKGROUND/AIM

There is concern that people who had COVID-19 will develop pulmonary fibrosis. Using mouse models, we compared pulmonary inflammation following injection of the spike protein of SARS-CoV-2 (COVID-19) to radiation-induced inflammation to demonstrate similarities between the two models. SARS-CoV-2 (COVID-19) induces inflammatory cytokines and stress responses, which are also common to ionizing irradiation-induced acute pulmonary damage. Cellular senescence, which is a late effect following exposure to SARS-CoV-2 as well as radiation, was investigated.

MATERIALS AND METHODS

We evaluated the effect of SARS-CoV-2 spike protein compared to ionizing irradiation in K18-hACE2 mouse lung, human lung cell lines, and in freshly explanted human lung. We measured reactive oxygen species, DNA double-strand breaks, stimulation of transforming growth factor-beta pathways, and cellular senescence following exposure to SARS-CoV-2 spike protein, irradiation or SARS-COV-2 and irradiation. We also measured the effects of the antioxidant radiation mitigator MMS350 following irradiation or exposure to SARS-CoV-2.

RESULTS

SARS-CoV-2 spike protein induced reactive oxygen species, DNA double-strand breaks, transforming growth factor-β signaling pathways, and senescence, which were exacerbated by prior or subsequent ionizing irradiation. The water-soluble radiation countermeasure, MMS350, reduced spike protein-induced changes.

CONCLUSION

In both the SARS-Co-2 and the irradiation mouse models, similar responses were seen indicating that irradiation or exposure to SARS-CoV-2 virus may lead to similar lung diseases such as pulmonary fibrosis. Combination of irradiation and SARS-CoV-2 may result in a more severe case of pulmonary fibrosis. Cellular senescence may explain some of the late effects of exposure to SARS-CoV-2 spike protein and to ionizing irradiation.

Low-dose radiation therapy for COVID-19 pneumonia: Comparison of dosimetry and life-time attributable risk of cancer with conventional AP-PA fields and bone marrow sparing VMAT

PURPOSE

Low-dose radiation therapy (LDRT) to lungs did show encouraging results in COVID-19 patients in some clinical trials. However, there has been some concern regarding the long-term risk of radiation-induced cancer (RIC). Compared to the conventional AP-PA field technique, volumetric modulated arc therapy (VMAT) can potentially reduce the dose to the marrow and other organs at risk (OARs) and thus minimize the risk of cancer. We designed a dosimetry study to study if VMAT can reduce the exposure to the marrow and other OAR doses and curtail the estimated life-time attributable risk (LAR) of cancer.

METHODS AND MATERIALS

We retrieved the computed tomography scan data of 10 patients (aged 40-60 years, median 48 years) who have been already treated for any malignancy in the region of the thorax. A dose of 1.0 Gy in single fraction was prescribed to both lungs. All the organs were delineated as per the established guidelines. The dosimetry achieved by the two plans was compared to find the difference. Mean OAR doses were used to estimate the LAR for both plans and compared.

RESULTS

Planning target volume coverage parameters like conformity index and homogeneity index were significantly better with VMAT (P value < 0.05 for all). The mean dose to most OARs was significantly lower with VMAT (P value < 0.05 for all). The mean dose to the marrow was significantly lower with VMAT (59.05 vs 81.9 cGy with P value < 0.05). The overall LAR was significantly lower with VMAT as compared to the conventional plan (0.357% vs 0.398%, P value < 0.05).

CONCLUSION

Compared to the conventional technique, VMAT provides better OAR dosimetry for lung irradiation (a prescription dose of 1.0 Gy or more) in COVID-19 pneumonia. VMAT significantly reduces the risk of RIC. We therefore suggest if lung LDRT is used for COVID-19 patients, VMAT is the preferred technique for a prescription dose of ≥1.0 Gy.

Interplay of immune modulation, adaptive response and hormesis: Suggestive of threshold for clinical manifestation of effects of ionizing radiation at low doses?

The health impacts of low-dose ionizing radiation exposures have been a subject of debate over the last three to four decades. While there has been enough evidence of "no adverse observable" health effects at low doses and low dose rates, the hypothesis of "Linear No Threshold" continues to rule and govern the principles of radiation protection and the formulation of regulations and public policies. In adopting this conservative approach, the role of the biological processes underway in the human body is kept at abeyance. This review consolidates the available studies that discuss all related biological pathways and repair mechanisms that inhibit the progression of deleterious effects at low doses and low dose rates of ionizing radiation. It is pertinent that, taking cognizance of these processes, there is a need to have a relook at policies of radiation protection, which as of now are too stringent, leading to undue economic losses and negative public perception about radiation.

Efficacy of low-dose lung radiotherapy in the management of COVID-19 patients: a randomised, open-label study

OBJECTIVE

Evaluate role of low-dose radiotherapy (LDRT) in COVID-19 pneumonia.

METHODS

Sixty-five patients 40 years or older tested positive for COVID-19 reverse transcriptase-polymerase chain reaction with mild to moderate acute respiratory distress syndrome (ARDS), were randomised 1:1, from 4 June 2021, to either best standard of care (control arm) according to the Indian Council of Medical Research guidelines or a single dose of LDRT (LDRT-0.5Gy) to both lungs along with best standard of care (experimental arm). The primary outcome was either progression to severe disease (PaO2/FiO2 ratio <100 mmHg) within 28 days of randomisation or all-cause mortality at 28 days. If the primary outcome could have been prevented, it was considered "favourable"; if not, it was considered "unfavourable."

RESULTS

Thirty-three patients were allocated to experimental arm, 32 to control arm. An intention to treat analysis was performed. Unfavourable outcome was seen in 5 (15.2%) patients in experimental arm, vs , 12 (37.5%) patients in control arm, odds of an unfavourable outcome in experimental arm were 0.3, 95% CI 0.09-0.97; two-sided p = 0.04. Four and five patients died in experimental and control arm, respectively. No radiation-induced toxicity was observed.

CONCLUSION

LDRT reduced the number of patients with unfavourable outcome at 28 days.

ADVANCES IN KNOWLEDGE

One of the few randomised studies showing reduced unfavourable outcome in mild to moderate ARDS COVID-19 patients receiving LDRT.CTRI/2021/06/034001, Clinical Trials Registry - India (ICMR-NIMS).

Noncancer Effects of Ionizing Radiation Exposure on the Eye, the Circulatory System and beyond: Developments made since the 2011 ICRP Statement on Tissue Reactions

For radiation protection purposes, noncancer effects with a threshold-type dose-response relationship have been classified as tissue reactions (formerly called nonstochastic or deterministic effects), and equivalent dose limits aim to prevent occurrence of such tissue reactions. Accumulating evidence demonstrates increased risks for several late occurring noncancer effects at doses and dose rates much lower than previously considered. In 2011, the International Commission on Radiological Protection (ICRP) issued a statement on tissue reactions to recommend a threshold of 0.5 Gy to the lens of the eye for cataracts and to the heart and brain for diseases of the circulatory system (DCS), independent of dose rate. Literature published thereafter continues to provide updated knowledge. Increased risks for cataracts below 0.5 Gy have been reported in several cohorts (e.g., including in those receiving protracted or chronic exposures). A dose threshold for cataracts is less evident with longer follow-up, with limited evidence available for risk of cataract removal surgery. There is emerging evidence for risk of normal-tension glaucoma and diabetic retinopathy, but the long-held tenet that the lens represents among the most radiosensitive tissues in the eye and in the body seems to remain unchanged. For DCS, increased risks have been reported in various cohorts, but the existence or otherwise of a dose threshold is unclear. The level of risk is less uncertain at lower dose and lower dose rate, with the possibility that risk per unit dose is greater at lower doses and dose rates. Target organs and tissues for DCS are also unknown, but may include heart, large blood vessels and kidneys. Identification of potential factors (e.g., sex, age, lifestyle factors, coexposures, comorbidities, genetics and epigenetics) that may modify radiation risk of cataracts and DCS would be important. Other noncancer effects on the radar include neurological effects (e.g., Parkinson's disease, Alzheimer's disease and dementia) of which elevated risk has increasingly been reported. These late occurring noncancer effects tend to deviate from the definition of tissue reactions, necessitating more scientific developments to reconsider the radiation effect classification system and risk management. This paper gives an overview of historical developments made in ICRP prior to the 2011 statement and an update on relevant developments made since the 2011 ICRP statement.

Low-dose radiation therapy suppresses viral pneumonia by enhancing broad-spectrum anti-inflammatory responses via transforming growth factor-β production

Low-dose radiation therapy (LDRT) can suppress intractable inflammation, such as that in rheumatoid arthritis, and is used for treating more than 10,000 rheumatoid arthritis patients annually in Europe. Several recent clinical trials have reported that LDRT can effectively reduce the severity of coronavirus disease (COVID-19) and other cases of viral pneumonia. However, the therapeutic mechanism of LDRT remains unelucidated. Therefore, in the current study, we aimed to investigate the molecular mechanism underlying immunological alterations in influenza pneumonia after LDRT. Mice were irradiated to the whole lung 1 day post-infection. The changes in levels of inflammatory mediators (cytokines and chemokines) and immune cell populations in the bronchoalveolar lavage (BALF), lungs, and serum were examined. LDRT-treated mice displayed markedly increased survival rates and reduced lung edema and airway and vascular inflammation in the lung; however, the viral titers in the lungs were unaffected. Levels of primary inflammatory cytokines were reduced after LDRT, and transforming growth factor-β (TGF-β) levels increased significantly on day 1 following LDRT. Levels of chemokines increased from day 3 following LDRT. Additionally, M2 macrophage polarization or recruitment was increased following LDRT. We found that LDRT-induced TGF-β reduced the levels of cytokines and polarized M2 cells and blocked immune cell infiltration, including neutrophils, in BALF. LDRT-induced early TGF-β production was shown to be a key regulator involved in broad-spectrum anti-inflammatory activity in virus-infected lungs. Therefore, LDRT or TGF-β may be an alternative therapy for viral pneumonia.

Considerations of Medical Preparedness to Assess and Treat Various Populations During a Radiation Public Health Emergency

During a radiological or nuclear public health emergency, given the heterogeneity of civilian populations, it is incumbent on medical response planners to understand and prepare for a potentially high degree of interindividual variability in the biological effects of radiation exposure. A part of advanced planning should include a comprehensive approach, in which the range of possible human responses in relation to the type of radiation expected from an incident has been thoughtfully considered. Although there are several reports addressing the radiation response for special populations (as compared to the standard 18-45-year-old male), the current review surveys published literature to assess the level of consideration given to differences in acute radiation responses in certain sub-groups. The authors attempt to bring clarity to the complex nature of human biology in the context of radiation to facilitate a path forward for radiation medical countermeasure (MCM) development that may be appropriate and effective in special populations. Consequently, the focus is on the medical (as opposed to logistical) aspects of preparedness and response. Populations identified for consideration include obstetric, pediatric, geriatric, males, females, individuals of different race/ethnicity, and people with comorbidities. Relevant animal models, biomarkers of radiation injury, and MCMs are highlighted, in addition to underscoring gaps in knowledge and the need for consistent and early inclusion of these populations in research. The inclusion of special populations in preclinical and clinical studies is essential to address shortcomings and is an important consideration for radiation public health emergency response planning. Pursuing this goal will benefit the population at large by considering those at greatest risk of health consequences after a radiological or nuclear mass casualty incident.

Aishwarya T A, Mohan DK, Nandhini K, Raavi V, Perumal V. Impact of X-radiation in the management of COVID-19 disease

Coronaviruses are a diverse group of viruses that infect both animals and humans. Even though the existence of coronavirus and its infection to humans is not new, the 2019-novel coronavirus (nCoV) caused a major burden to individuals and society i.e., anxiety, fear of infection, extreme competition for hospitalization, and more importantly financial liability. The nCoV infection/disease diagnosis was based on non-specific signs and symptoms, biochemical parameters, detection of the virus using reverse-transcription polymerase chain reaction (RT-PCR), and X-ray-based imaging. This review focuses on the consolidation of potentials of X-ray-based imaging modality [chest-X radiography (CXR) and chest computed tomography (CT)] and low-dose radiation therapy (LDRT) for screening, severity, and management of COVID-19 disease. Reported studies suggest that CXR contributed significantly toward initial rapid screening/diagnosis and CT- imaging to monitor the disease severity. The chest CT has high sensitivity up to 98% and low specificity for diagnosis and severity of COVID-19 disease compared to RT-PCR. Similarly, LDRT compliments drug therapy in the early recovery/Less hospital stays by maintaining the physiological parameters better than the drug therapy alone. All the results undoubtedly demonstrated the evidence that X-ray-based technology continues to evolve and play a significant role in human health care even during the pandemic.

Covid-19 and radiotherapy: a systematic review after 2 years of pandemic

Introduction

Following the Covid-19 pandemic spread, changes in clinical practice were necessary to limit the pandemic diffusion. Also, oncological practice has undergone changes with radiotherapy (RT) treatments playing a key role.Although several experiences have been published, the aim of this review is to summarize the current evidence after 2 years of pandemic to provide useful conclusions for clinicians.

Methods

A Pubmed/MEDLINE and Embase systematic review was conducted. The search strategy was "Covid AND Radiotherapy" and only original articles in the English language were considered.

Results

A total of 2.733 papers were obtained using the mentioned search strategy. After the complete selection process, a total of 281 papers were considered eligible for the analysis of the results.

Discussion

RT has played a key role in Covid-19 pandemic as it has proved more resilient than surgery and chemotherapy. The impact of the accelerated use of hypofractionated RT and telemedicine will make these strategies central also in the post-pandemic period.

Pre-clinic study of radiopharmaceutical for Covid-19 inactivation: Dose distribution with Monte Carlo Simulation

Monte Carlo simulation method and Nuclear Medicine MIRD method were used to evaluate the effect of radiopharmaceuticals on Covid-19 disease. The mean absorbed organ dose in the target organ and gamma radiation emitter attenuation properties such as linear attenuation coefficients, energy absorption build-up factors (EABF), exposure build-up factors (EBF), and relative dose distributions (RDD) were examined. The results showed that radiopharmaceuticals containing gamma radiation emitters which are densely ionizing charged particles induced membrane damage and produced protein damage.

Preliminary Approach to Implementing a COVID-19 Thoracic Radiation Therapy Program

The value of low-dose whole thoracic radiation therapy (LD-WTRT) for SARS-CoV-2 (COVID-19) pneumonia is unknown. Should ongoing clinical trials demonstrate that LD-WTRT proves effective for COVID-19 pneumonia recovery, widespread rapid implementation will be helpful globally. Our aim was to outline a pragmatic process for safe and efficient administration of LD-WTRT to patients with COVID-19 pneumonia that could be implemented successfully in a community hospital setting based on participation in the PreVent clinical trial of LD-WTRT.

Low-dose radiotherapy for COVID-19 pneumonia and cancer: summary of a recent symposium and future perspectives

The lessons learned from the Coronavirus Disease 2019 (COVID-19) pandemic are numerous. Low dose radiotherapy (LDRT) was used in the pre-antibiotic era as treatment for bacterially/virally associated pneumonia. Motivated in part by these historic clinical and radiobiological data, LDRT for treatment of COVID-19-associated pneumonia was proposed in early 2020. Although there is a large body of epidemiological and experimental data pointing to effects such as cancer at low doses, there is some evidence of beneficial health effects at low doses. It has been hypothesized that low dose radiation could be combined with immune checkpoint therapy to treat cancer. We shall review here some of these old radiobiological and epidemiological data, as well as the newer data on low dose radiation and stimulated immune response and other relevant emerging data. The paper includes a summary of several oral presentations given in a Symposium on "Low dose RT for COVID and other inflammatory diseases" as part of the 67th Annual Meeting of the Radiation Research Society, held virtually 3-6 October 2021.

Effectiveness of low-dose radiation therapy in COVID-19 patients globally: A systematic review

Background: Novel Corona Virus Disease 2019 (COVID-19) can affect multiple organs, including the lungs, resulting in pneumonia. Apart from steroids, other anti-COVID drugs that have been studied appear to have little or no effect on COVID-19 pneumonia. There is a well-known history of inflammatory disease, including pneumonia, treated with low-dose radiation therapy (LDRT). It reduces the production of proinflammatory cytokines, Interleukin-1a (IL-1a), and leukocyte recruitment.   Methods: A comprehensive literature search was conducted using PubMed, Scopus, Embase, CINAHL, and Google Scholar, with keywords such as "radiotherapy," "low-dose radiation therapy," "low-dose irradiation," "covid-19 pneumonia," "SARS-CoV-2 pneumonia," and "covid pneumonia." with additional filters for human studies and customized articles in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. We reviewed randomized controlled trials, quasi-experimental studies, cohort, case-control, and cross-sectional studies with a clearly defined intervention, including low-dose radiotherapy alone or in combination with any therapy to treat COVID-19 pneumonia from December 2019 to May 2021. Patients receiving standard or high-dose radiotherapy, including for other diseases, were excluded. Zotero software was used to collect and organize research from various databases, remove duplicates, extract relevant data, and record decisions. Participants' demographics and baseline status were obtained from the full-text articles along with the intervention's outcome/effect on patient status.  Results: Four studies with 61 participants that met the inclusion criteria were included. One was a double-blind randomized controlled trial, one a non-randomized trial, while the other two were single-arm clinical trials. Low-dose radiation therapy did not show any significant improvement in COVID-19 patients.  Conclusion: Only two studies included in this review demonstrated an improvement in inflammatory markers; however, patients were also given steroids or other drugs. Therefore, the confounding effects must be considered before drawing conclusions. This systematic review does not support mortality benefit, clinical course improvement, or imaging changes with LDRT.

A model of infection and immune response to low dose radiation

PURPOSE

Low dose radiation therapy (LDRT) using doses in the range of 30-150 cGy has been proposed as a means of mitigating the pneumonia associated with COVID-19. However, preliminary results from ongoing clinical trials have been mixed. The aim of this work is to develop a mathematical model of the viral infection and associated systemic inflammation in a patient based on the time evolution of the viral load. The model further proposes an immunomodulatory response to LDRT based on available data. Inflammation kinetics are then explored and compared to clinical results.

METHODS

The time evolution of a viral infection, inflammatory signaling factors, and inflammatory response are modeled by a set of coupled differential equations. Adjustable parameters are taken from the literature where available and otherwise iteratively adjusted to fit relevant data. Simple functions modeling both the suppression of pro-inflammatory signal factors and the enhancement of anti-inflammatory factors in response to low doses of radiation are developed. The inflammation response is benchmarked against C-reactive protein (CRP) levels measured for cohorts of patients with severe COVID-19.

RESULTS

The model fit the time-evolution of viral load data, cytokine data, and inflammation (CRP) data. When LDRT was applied early, the model predicted a reduction in peak inflammation consistent with the difference between the non-surviving and surviving cohorts. This reduction of peak inflammation diminished as the application of LDRT was delayed.

CONCLUSION

The model tracks the available data on viral load, cytokine levels, and inflammatory biomarkers well. An LDRT effect is large enough in principle to provide a life-saving immunomodulatory effect, though patients treated with LDRT already near the peak of their inflammation trajectory are unlikely to see drastic reductions in that peak. This result potentially explains some discrepancies in the preliminary clinical trial data.

Low-Dose Lung Radiation Therapy for COVID-19 Lung Disease: A Preclinical Efficacy Study in a Bleomycin Model of Pneumonitis

PURPOSE

Low-dose whole lung radiation therapy (LDLR) has been proposed as a treatment for patients with acute respiratory distress syndrome associated with SARS-CoV-2 infection, and clinical trials are underway. There is an urgent need for preclinical evidence to justify this approach and inform dose, scheduling, and mechanisms of action.

METHODS AND MATERIALS

Female C57BL/6 mice were treated with intranasal bleomycin sulfate (7.5 or 11.25 units/kg, day 0) and then exposed to whole lung radiation therapy (0.5, 1.0, or 1.5 Gy, or sham; day 3). Bodyweight was measured daily, and lung tissue was harvested for histology and flow cytometry on day 10. Computed tomography lung imaging was performed before radiation (day 3) and pre-endpoint (day 10).

RESULTS

Bleomycin caused pneumonitis of variable severity, which correlated with weight loss. LDLR at 1.0 Gy was associated with a significant increase in the proportion of mice recovering to 98% of initial bodyweight, and a proportion of these mice exhibited less severe histopathologic lung changes. Mice experiencing moderate initial weight loss were more likely to respond to LDLR than those experiencing severe initial weight loss. In addition, LDLR (1.0 Gy) significantly reduced bleomycin-induced increases in interstitial macrophages, CD103+ dendritic cells (DCs), and neutrophil-DC hybrids. Overall, bleomycin-treated mice exhibited significantly higher percentages of nonaerated lung in left than right lungs, and LDLR (1.0 Gy) limited further reductions in aerated lung volume in right but not left lungs. LDLR at 0.5 and 1.5 Gy did not improve bodyweight, flow cytometric, or radiologic readouts of bleomycin-induced pneumonitis.

CONCLUSIONS

Our data support the concept that LDLR can ameliorate acute inflammatory lung injury, identify 1.0 Gy as the most effective dose, and provide evidence that it is more effective in the context of moderate than severe pneumonitis. Mechanistically, LDLR at 1.0 Gy significantly suppressed bleomycin-induced accumulation of pulmonary interstitial macrophages, CD103+ DCs, and neutrophil-DC hybrids.

Whole-lung low-dose radiation therapy (LD-RT) for non-intubated oxygen-dependent patients with COVID-19-related pneumonia receiving dexamethasone and/or remdesevir

BACKGROUND

Low-dose radiotherapy (LD-RT) has produced anti-inflammatory effects in both animal models and early human trials of COVID-19-related pneumonia. The role of whole-lung LD-RT within existing treatment paradigms merits further study.

METHODS

A phase II prospective trial studied the addition of LD-RT to standard drug treatments. Hospitalized and oxygen-dependent patients receiving dexamethasone and/or remdesevir were treated with 1.5 Gy whole-lung LD-RT and compared to a blindly-matched contemporaneous control cohort.

RESULTS

Of 40 patients evaluated, 20 received drug therapy combined with whole-lung LD-RT and 20 without LD-RT. Intubation rates were 14% with LD-RT compared to 32% without (p = 0.09). Intubation-free survival was 77% vs. 68% (p = 0.17). Biomarkers of inflammation (C-reactive protein, p = 0.02) and cardiac injury (creatine kinase, p < 0.01) declined following LD-RT compared to controls. Mean time febrile was 1.4 vs 3.3 days, respectively (p = 0.14). Significant differences in clinical recovery (7.5 vs. 7 days, p = 0.37) and radiographic improvement (p = 0.72) were not detected. On subset analysis, CRP decline following LD-RT was predictive of recovery without intubation compared to controls (0% vs. 31%, p = 0.04), freedom from prolonged hospitalizations (21+ days) (0% vs. 31%, p = 0.04), and decline in oxygenation burden (56% reduction, p = 0.06). CRP decline following 1st drug therapy was not similarly predictive of outcome in controls (p = 0.36).

CONCLUSIONS

Adding LD-RT to standard drug treatments reduced biomarkers of inflammation and cardiac injury in COVID-19 patients and may have reduced intubation. Durable CRP decline following LD-RT predicted especially favorable recovery, freedom from intubation, reduction in prolonged hospitalization, and reduced oxygenation burden. A confirmatory randomized trial is now ongoing.

CLINICAL TRIAL REGISTRATION

NCT04366791.

A million persons, a million dreams: a vision for a national center of radiation epidemiology and biology

BACKGROUND

Epidemiologic studies of radiation-exposed populations form the basis for human safety standards. They also help shape public health policy and evidence-based health practices by identifying and quantifying health risks of exposure in defined populations. For more than a century, epidemiologists have studied the consequences of radiation exposures, yet the health effects of low levels delivered at a low-dose rate remain equivocal.

MATERIALS AND METHODS

The Million Person Study (MPS) of U.S. Radiation Workers and Veterans was designed to examine health effects following chronic exposures in contrast with brief exposures as experienced by the Japanese atomic bomb survivors. Radiation associations for rare cancers, intakes of radionuclides, and differences between men and women are being evaluated, as well as noncancers such as cardiovascular disease and conditions such as dementia and cognitive function. The first international symposium, held November 6, 2020, provided a broad overview of the MPS. Representatives from four U.S. government agencies addressed the importance of this research for their respective missions: U.S. Department of Energy (DOE), the Centers for Disease Control and Prevention (CDC), the U.S. Department of Defense (DOD), and the National Aeronautics and Space Administration (NASA). The major components of the MPS were discussed and recent findings summarized. The importance of radiation dosimetry, an essential feature of each MPS investigation, was emphasized.

RESULTS

The seven components of the MPS are DOE workers, nuclear weapons test participants, nuclear power plant workers, industrial radiographers, medical radiation workers, nuclear submariners, other U.S. Navy personnel, and radium dial painters. The MPS cohorts include tens of thousands of workers with elevated intakes of alpha particle emitters for which organ-specific doses are determined. Findings to date for chronic radiation exposure suggest that leukemia risk is lower than after acute exposure; lung cancer risk is much lower and there is little difference in risks between men and women; an increase in ischemic heart disease is yet to be seen; esophageal cancer is frequently elevated but not myelodysplastic syndrome; and Parkinson's disease may be associated with radiation exposure.

CONCLUSIONS

The MPS has provided provocative insights into the possible range of health effects following low-level chronic radiation exposure. When the 34 MPS cohorts are completed and combined, a powerful evaluation of radiation-effects will be possible. This final article in the MPS special issue summarizes the findings to date and the possibilities for the future. A National Center for Radiation Epidemiology and Biology is envisioned.

Could pulmonary low-dose radiation therapy be an alternative treatment for patients with COVID-19 pneumonia? Preliminary results of a multicenter SEOR-GICOR nonrandomized prospective trial (IPACOVID trial)

PURPOSE

To evaluate the efficacy and safety of lung low-dose radiation therapy (LD-RT) for pneumonia in patients with coronavirus disease 2019 (COVID-19).

MATERIALS AND METHODS

Inclusion criteria comprised patients with COVID-19-related moderate-severe pneumonia warranting hospitalization with supplemental O2 and not candidates for admission to the intensive care unit because of comorbidities or general status. All patients received single lung dose of 0.5 Gy. Respiratory and systemic inflammatory parameters were evaluated before irradiation, at 24 h and 1 week after LD-RT. Primary endpoint was increased in the ratio of arterial oxygen partial pressure (PaO2) or the pulse oximetry saturation (SpO2) to fractional inspired oxygen (FiO2) ratio of at least 20% at 24 h with respect to the preirradiation value.

RESULTS

Between June and November 2020, 36 patients with COVID-19 pneumonia and a mean age of 84 years were enrolled. Seventeen were women and 19 were men and all of them had comorbidities. All patients had bilateral pulmonary infiltrates on chest X‑ray. All patients received dexamethasone treatment. Mean SpO2 pretreatment value was 94.28% and the SpO2/FiO2 ratio varied from 255 mm Hg to 283 mm Hg at 24 h and to 381 mm Hg at 1 week, respectively. In those who survived (23/36, 64%), a significant improvement was observed in the percentage of lung involvement in the CT scan at 1 week after LD-RT. No adverse effects related to radiation treatment have been reported.

CONCLUSIONS

LD-RT appears to be a feasible and safe option in a population with COVID-19 bilateral interstitial pneumonia in the presence of significant comorbidities.

Overcoming Barriers to Radiation Oncology Access in Low-Resource Settings in the United States

Providing high-quality radiation therapy in medically underserved, low-resource environments can be challenging in the United States. During the American Society of Radiation Oncology 2020 Annual Meeting, the American Society for Radiation Oncology Committee on Health Equity, Diversity, and Inclusion hosted 4 radiation oncologists from both academic and community practices in an educational session. Speakers discussed creative ways to overcome barriers to equitable cancer care and outcomes for their vulnerable patient populations in both rural and urban settings. Successful tactics have included applying for state-sponsored grants, lobbying hospital leadership for equipment upgrades, implementing quality improvement programs specifically targeting the needs of the patient population, studying novel hypofractionation schedules, monitoring toxicities using wearable devices, and expanding transportation options.

Role of Mitochondria in Radiation Responses: Epigenetic, Metabolic, and Signaling Impacts

Until recently, radiation effects have been considered to be mainly due to nuclear DNA damage and their management by repair mechanisms. However, molecular biology studies reveal that the outcomes of exposures to ionizing radiation (IR) highly depend on activation and regulation through other molecular components of organelles that determine cell survival and proliferation capacities. As typical epigenetic-regulated organelles and central power stations of cells, mitochondria play an important pivotal role in those responses. They direct cellular metabolism, energy supply and homeostasis as well as radiation-induced signaling, cell death, and immunological responses. This review is focused on how energy, dose and quality of IR affect mitochondria-dependent epigenetic and functional control at the cellular and tissue level. Low-dose radiation effects on mitochondria appear to be associated with epigenetic and non-targeted effects involved in genomic instability and adaptive responses, whereas high-dose radiation effects (>1 Gy) concern therapeutic effects of radiation and long-term outcomes involving mitochondria-mediated innate and adaptive immune responses. Both effects depend on radiation quality. For example, the increased efficacy of high linear energy transfer particle radiotherapy, e.g., C-ion radiotherapy, relies on the reduction of anastasis, enhanced mitochondria-mediated apoptosis and immunogenic (antitumor) responses.

Whole lung irradiation as a novel treatment for COVID-19: Interim results of an ongoing phase 2 trial in India

BACKGROUND AND PURPOSE

The main cause of death in COVID-19 pneumonia is acute respiratory distress syndrome which is preceded by massive cytokine release. Low-dose radiation therapy (LDRT) has anti-inflammatory and immunomodulatory effects that can interfere with the inflammatory cascade, reducing the severity of associated cytokine release.

MATERIAL & METHODS

25 patients with RT-PCR proven COVID-19 pneumonia were enrolled between November 2020 and May 2021. All patients had SpO2 < 94 % on room air, respiratory frequency > 24/min and SpO2/FiO2 ratio (SF ratio) of >89 but <357. Patients were treated according to standard COVID-19 management guidelines along with single fraction LDRT of 0.5 Gy to bilateral whole lungs within 10 days of symptom onset and 5 days of hospital admission.

RESULTS

LDRT was well tolerated by all patients. There was a statistically significant improvement in oxygenation as given by the SF ratio between pre-RT and day 2 (p < 0.05), day 3 (p < 0.001) and day 7 (p < 0.001) post RT. Demand for supplemental oxygen showed statistically significant reduction between pre-RT and day 2 (p < 0.05), day 3 (p < 0.001), day 7 (p < 0.001) post RT. 88 % patients attained clinical recovery within 10 days post LDRT and median time to hospital discharge from day of LDRT was 6 days. Three patients deteriorated and died.

CONCLUSION

As per our initial experience, LDRT appears to be a promising modality of treatment with rapid relief of respiratory distress in selected patients with moderate to severe COVID-19 pneumonia. This translates to early clinical recovery and hospital discharge in the selected patient group.

Low-dose radiation therapy for COVID-19 pneumonia: a pilot study

Objectives:

The World Health Organization (WHO) has declared coronavirus disease 2019 (COVID-19) as pandemic in March 2020. Currently there is no specific effective treatment for COVID-19. The major cause of death in COVID-19 is severe pneumonia leading to respiratory failure. Radiation in low doses (<100 cGy) has been known for its anti-inflammatory effect and therefore, low dose radiation therapy (LDRT) to lungs can potentially mitigate the severity of pneumonia and reduce mortality. We conducted a pilot trial to study the feasibility and clinical efficacy of LDRT to lungs in the management of patients with COVID-19.

Methods:

From June to Aug 2020, we enrolled 10 patients with COVID-19 having moderate to severe risk disease [National Early Warning Score (NEWS) of ≥5]. Patients were treated as per the standard COVID-19 management guidelines along with LDRT to both lungs with a dose of 70cGy in single fraction. Response assessment was done based on the clinical parameters using the NEWS.

Results:

All patients completed the prescribed treatment. Nine patients had complete clinical recovery mostly within a period ranging from 3 to 7 days. One patient, who was a known hypertensive, showed clinical deterioration and died 24 days after LDRT. No patients showed the signs of acute radiation toxicity.

Conclusion:

The results of our pilot study suggest that LDRT is feasible in COVID-19 patients having moderate to severe disease. Its clinical efficacy may be tested by conducting randomized controlled trials.

Advances in knowledge:

LDRT has shown promising results in COVID-19 pneumonia and should be researched further through randomized controlled trials.

Lung Cancer and Heart Disease Risks Associated With Low-Dose Pulmonary Radiotherapy to COVID-19 Patients With Different Background Risks

PURPOSE

The respiratory disease COVID-19 reached global pandemic status in 2020. Excessive inflammation is believed to result in the most severe symptoms and death from this disease. Because treatment options for patients with severe COVID-19 related pulmonary symptoms remain limited, whole-lung low-dose radiation therapy is being evaluated as an anti-inflammatory modality. However, there is concern about the long-term risks associated with low-dose pulmonary irradiation. To help quantify the benefit-risk balance of low-dose radiation therapy for COVID-19, we estimated radiation-induced lifetime risks of both lung cancer and heart disease (major coronary events) for patients of different sexes, treated at ages 50 to 85, with and without other relevant risk factors (cigarette smoking and baseline heart disease risk).

METHODS AND MATERIALS

These estimates were generated by combining state-of-the-art radiation risk models for lung cancer and for heart disease together with background lung cancer and heart disease risks and age/sex-dependent survival probabilities for the U.S.

POPULATION

RESULTS

Estimated absolute radiation-induced risks were generally higher for lung cancer compared with major coronary events. The highest estimated lifetime radiation-induced lung cancer risks were approximately 6% for female smokers treated between ages 50 and 60. The highest estimated radiation-induced heart disease risks were approximately 3% for males or females with high heart disease risk factors and treated between ages 50 and 60.

CONCLUSIONS

The estimated summed lifetime risk of lung cancer and major coronary events reached up to 9% in patients with high baseline risk factors. Predicted lung cancer and heart disease risks were lowest in older nonsmoking patients and patients with few cardiac risk factors. These long-term risk estimates, along with consideration of possible acute reactions, should be useful in assessing the benefit-risk balance for low-dose radiation therapy to treat severe COVID-19 pulmonary symptoms, and suggest that background risk factors, particularly smoking, should be taken into account in such assessments.

COVID-19: The Disease, the Immunological Challenges, the Treatment with Pharmaceuticals and Low-Dose Ionizing Radiation

The year 2020 will be carved in the history books-with the proliferation of COVID-19 over the globe and with frontline health workers and basic scientists worldwide diligently fighting to alleviate life-threatening symptoms and curb the spread of the disease. Behind the shocking prevalence of death are countless families who lost loved ones. To these families and to humanity as a whole, the tallies are not irrelevant digits, but a motivation to develop effective strategies to save lives. However, at the onset of the pandemic, not many therapeutic choices were available besides supportive oxygen, anti-inflammatory dexamethasone, and antiviral remdesivir. Low-dose radiation (LDR), at a much lower dosage than applied in cancer treatment, re-emerged after a 75-year silence in its use in unresolved pneumonia, as a scientific interest with surprising effects in soothing the cytokine storm and other symptoms in severe COVID-19 patients. Here, we review the epidemiology, symptoms, immunological alterations, mutations, pharmaceuticals, and vaccine development of COVID-19, summarizing the history of X-ray irradiation in non-COVID diseases (especially pneumonia) and the currently registered clinical trials that apply LDR in treating COVID-19 patients. We discuss concerns, advantages, and disadvantages of LDR treatment and potential avenues that may provide empirical evidence supporting its potential use in defending against the pandemic.

Low dose ionizing radiation and the immune response: what is the role of non-targeted effects?

OBJECTIVES

This review aims to trace the historical narrative surrounding the low dose effects of radiation on the immune system and how our understanding has changed from the beginning of the 20th century to now. The particular focus is on the non-targeted effects (NTEs) of low dose ionizing radiation (LDIR) which are effects that occur when irradiated cells emit signals that cause effects in the nearby or distant non-irradiated cells known as radiation induced bystander effect (RIBE). Moreover, radiation induced genomic instability (RIGI) and abscopal effect (AE) also regarded as NTE. This was prompted by our recent discovery that ultraviolet A (UVA) photons are emitted by the irradiated cells and that these photons can trigger NTE such as the RIBE in unirradiated recipients of these photons. Given the well-known association between UV radiation and the immune response, where these biophotons may pose as bystander signals potentiating processes in deep tissues as a consequence of LDIR, it is timely to review the field with a fresh lens. Various pathways and immune components that contribute to the beneficial and adverse types of modulation induced by LDR will also be revisited.

CONCLUSION

There is limited evidence for LDIR induced immune effects by way of a non-targeted mechanism in biological tissue. The literature examining low to medium dose effects of ionizing radiation on the immune system and its components is complex and controversial. Early work was compromised by lack of good dosimetry while later work mainly looks at the involvement of immune response in radiotherapy. There is a lack of research in the LDIR/NTE field focusing on immune response although bone marrow stem cells and lineages were critical in the identification and characterization of NTE where effects like RIGI and RIBE were heavily researched. This may be in part, a result of the difficulty of isolating NTE in whole organisms which are essential for good immune response studies. Models involving inter organism transmission of NTE are a promising route to overcome these issues.

All for one, though not one for all: team players in normal tissue radiobiology

PURPOSE

As part of the special issue on 'Women in Science', this review offers a perspective on past and ongoing work in the field of normal (non-cancer) tissue radiation biology, highlighting the work of many of the leading contributors to this field of research. We discuss some of the hypotheses that have guided investigations, with a focus on some of the critical organs considered dose-limiting with respect to radiation therapy, and speculate on where the field needs to go in the future.

CONCLUSIONS

The scope of work that makes up normal tissue radiation biology has and continues to play a pivotal role in the radiation sciences, ensuring the most effective application of radiation in imaging and therapy, as well as contributing to radiation protection efforts. However, despite the proven historical value of preclinical findings, recent decades have seen clinical practice move ahead with altered fractionation scheduling based on empirical observations, with little to no (or even negative) supporting scientific data. Given our current appreciation of the complexity of normal tissue radiation responses and their temporal variability, with tissue- and/or organ-specific mechanisms that include intra-, inter- and extracellular messaging, as well as contributions from systemic compartments, such as the immune system, the need to maintain a positive therapeutic ratio has never been more urgent. Importantly, mitigation and treatment strategies, whether for the clinic, emergency use following accidental or deliberate releases, or reducing occupational risk, will likely require multi-targeted approaches that involve both local and systemic intervention. From our personal perspective as five 'Women in Science', we would like to acknowledge and applaud the role that many female scientists have played in this field. We stand on the shoulders of those who have gone before, some of whom are fellow contributors to this special issue.

Increased Radiation Dose Exposure in Thoracic Computed Tomography in Patients with Covid-19

The CT manifestation of COVID-19 patients is now well known and essentially reflects pathological changes in the lungs. Actually, there is insufficient knowledge on the long-term outcomes of this new disease, and several chest CTs might be necessary to evaluate the outcomes. The aim of this study is to evaluate the radiation dose for chest CT scans in COVID-19 patients compared to a cohort with pulmonary infectious diseases at the same time of the previous year to value if there is any modification of exposure dose. The analysis of our data shows an increase in the overall mean dose in COVID-19 patients compared with non-COVID-19 patients. In our results, the higher dose increase occurs in the younger age groups (+86% range 21–30 years and +67% range 31–40 years). Our results show that COVID-19 patients are exposed to a significantly higher dose of ionizing radiation than other patients without COVID infectious lung disease, and especially in younger age groups, although some authors have proposed the use of radiotherapy in these patients, which is yet to be validated. Our study has limitations: the use of one CT machine in a single institute and a limited number of patients.

Acute Radiation Syndrome and the Microbiome: Impact and Review

Study of the human microbiota has been a centuries-long endeavor, but since the inception of the National Institutes of Health (NIH) Human Microbiome Project in 2007, research has greatly expanded, including the space involving radiation injury. As acute radiation syndrome (ARS) is multisystemic, the microbiome niches across all areas of the body may be affected. This review highlights advances in radiation research examining the effect of irradiation on the microbiome and its potential use as a target for medical countermeasures or biodosimetry approaches, or as a medical countermeasure itself. The authors also address animal model considerations for designing studies, and the potential to use the microbiome as a biomarker to assess radiation exposure and predict outcome. Recent research has shown that the microbiome holds enormous potential for mitigation of radiation injury, in the context of both radiotherapy and radiological/nuclear public health emergencies. Gaps still exist, but the field is moving forward with much promise.

Low dose radiation therapy for severe COVID-19 pneumonia: a randomized double-blind study

PURPOSE

The morbidity and mortality of patients requiring mechanical ventilation for coronavirus disease 2019 (COVID-19) pneumonia is considerable. We studied the use of whole-lung low dose radiation therapy (LDRT) in this patient cohort.

METHODS AND MATERIALS

Patients admitted to the intensive care unit (ICU) and requiring mechanical ventilation for COVID-19 pneumonia were included in this randomized double-blind study. Patients were randomized to 1 Gy whole-lung LDRT or sham irradiation (sham-RT). Treatment group allocation was concealed from patients and ICU clinicians, who treated patients according to the current standard of care. Patients were followed for the primary endpoint of ventilator-free days (VFDs) at day 15 post-intervention. Secondary endpoints included overall survival, as well as changes in oxygenation and inflammatory markers.

RESULTS

Twenty-two patients were randomized to either whole-lung LDRT or sham-RT between November and December 2020. Patients were generally elderly and comorbid, with a median age of 75 years in both arms. No difference in 15-day VFDs was observed between groups (p = 1.00), with a median of 0 days (range, 0-9) in the LDRT arm, and 0 days (range, 0-13) in the sham-RT arm. Overall survival at 28 days was identical at 63.6% (95%CI, 40.7-99.5%) in both arms (p = 0.69). Apart from a more pronounced reduction in lymphocyte counts following LDRT (p < 0.01), analyses of secondary endpoints revealed no significant differences between the groups.

CONCLUSIONS

Whole-lung LDRT failed to improve clinical outcomes in critically ill patients requiring mechanical ventilation for COVID-19 pneumonia.

Clinician Attitudes to Using Low-Dose Radiation Therapy to Treat COVID-19 Lung Disease

PURPOSE

Current treatments for coronavirus disease 2019 (COVID-19) lung disease have limited efficacy. Low-dose radiation therapy (LDRT) has received both interest and criticism as a potential treatment for this condition. In this qualitative study we explored clinicians' perspectives to identify barriers to testing LDRT in clinical trials and implementing it in clinical practice.

METHODS AND MATERIALS

Semistructured interviews were undertaken with 6 clinicians from 3 medical disciplines. Interviews were recorded, transcribed verbatim, and analyzed thematically, using a framework approach. Common themes regarding barriers to using LDRT for COVID-19 lung disease were identified from the data.

RESULTS

Three categories of barriers emerged: (1) the potential to do harm to the patient, including difficulty in predicting harm and lack of existing data to inform quantification of risks; (2) the feasibility of trialing this novel treatment strategy in the clinical setting, in particular trial design and recruitment, patient selection and buy-in from relevant clinician groups; and (3) the logistics of delivering the treatment, in particular risks of transmission to other patients and resources required for patient transfer.

CONCLUSIONS

This study identified several barriers that may impede the evaluation and subsequent implementation of LDRT as a treatment for COVID-19 lung disease, from the perspectives of clinicians in 3 relevant specialties. By documenting and articulating these concerns, we hope to enhance discussion of why these barriers exist, and enable them to be addressed in a proactive manner to facilitate research into the potential benefits of radiation treatment for patients with COVID-19 lung disease going forward.

Immunomodulatory Low-Dose Whole-Lung Radiation for Patients with Coronavirus Disease 2019-Related Pneumonia

PURPOSE

Phase 1 clinical trials have established low-dose, whole-lung radiation therapy (LD-RT) as safe for patients with coronavirus disease 2019 (COVID-19)-related pneumonia. By focally dampening cytokine hyperactivation, LD-RT may improve disease outcomes through immunomodulation.

METHODS AND MATERIALS

Patients with COVID-19-related pneumonia were treated with 1.5 Gy whole-lung LD-RT, followed for 28 days or until hospital discharge, and compared with age- and comorbidity-matched controls meeting identical disease severity criteria. Eligible patients were hospitalized, severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) positive, had radiographic consolidations, and required supplemental oxygen but had not rapidly declined on admission or before drug therapy or LD-RT. Efficacy endpoints were time to clinical recovery, radiographic improvement, and biomarker response.

RESULTS

Ten patients received whole-lung LD-RT between April 24 and May 24, 2020 and were compared with 10 control patients blindly matched by age and comorbidity. Six controls received COVID-19 drug therapies. Median time to clinical recovery was 12 days in the control cohort compared with 3 days in the LD-RT cohort (hazard ratio 2.9, P = .05). Median time to hospital discharge (20 vs 12 days, P = .19) and intubation rates (40% vs 10%, P = .12) in the control and LD-RT cohorts were compared. Median time from admission to recovery was 10 versus 13 days (P = .13). Hospital duration average was 19 versus 22.6 days (P = .53). Average hospital days on supplemental oxygen of any duration was 13.1 versus 14.7 days (P = .69). Average days with a documented fever was 1 versus 4.3 days (P = .12). Twenty-eight-day overall survival was 90% for both cohorts. The LD-RT cohort trended toward superior rates of improved radiographs (P = .12) and delirium (P < .01). Statistically significant reductions were observed in numerous hematologic, cardiac, hepatic, and inflammatory markers.

CONCLUSIONS

A prospective cohort of predominantly elderly hospitalized patients with COVID-19-related pneumonia were recovered to room air quicker than age- and comorbidity-matched controls, with trending or significant improvements in delirium, radiographs, and biomarkers, and no significant acute toxicity. Low-dose, whole-lung radiation for patients with COVID-19-related pneumonia appears safe and may be an effective immunomodulatory treatment. Larger prospective randomized trials are needed to define the efficacy of LD-RT for COVID-19.

Low Doses of Radiation Increase the Immunosuppressive Profile of Lung Macrophages During Viral Infection and Pneumonia

Purpose

Severe pneumonia and acute respiratory distress syndrome (ARDS) have been described in patients with severe coronavirus disease 2019 (COVID-19). Recently, early clinical data reported the feasibility of low doses of radiation therapy (RT) in the treatment of ARDS in patients with severe COVID-19. However, the involved mechanisms remained unknown.

Methods and Materials

Here, we used airways-instilled lipopolysaccharide (LPS) and influenza virus (H1N1) as murine models of pneumonia, and toll-like receptor (TLR)-3 stimulation in human lung macrophages.

Results

Low doses of RT (0.5-1 Gray) decreased LPS-induced pneumonia, and increased the percentage of nerve- and airway-associated macrophages producing interleukin (IL) 10. During H1N1 viral infection, we observed decreased lung tissue damage and immune cell infiltration in irradiated animals. Low doses of RT increased IL-10 production by infiltrating immune cells into the lung. Irradiation of TLR-3 ligand-stimulated human lung macrophages ex vivo increased IL-10 secretion and decreased interferon γ production in the culture supernatant. The percentage of human lung macrophages producing IL-6 was also decreased.

Conclusions

Our data highlight a mechanism by which low doses of RT regulate lung inflammation and skew lung macrophages toward an anti-inflammatory profile. These data provide a preclinical mechanistic support to clinical trials evaluating low doses of RT, such as COVID-19-induced ARDS.

Low-dose radiotherapy (LD-RT) for COVID-19-induced pneumopathy: a worth considering approach

PURPOSE

It seems that 2020 would be always remembered by the name of novel coronavirus (designated as SARS-CoV-2), which exerted its deteriorating effects on the health care, economy, education, and political relationships. In August 2020 more than eight hundred thousand patients lost their lives due to acute respiratory syndrome. In the limited list of therapeutic approaches, the effectiveness of low-dose radiation therapy (LD-RT) for curing inflammatory-related diseases have sparkled a light that probably this approach would bring promising advantages for COVID-19 patients. LD-RT owns its reputation from its ability to modulate the host inflammatory responses by blocking the production of pro-inflammatory cytokines and hampering the activity of leukocytes. Moreover, the cost-effective and availability of this method allow it to be applied to a large number of patients, especially those who could not receive anti-IL-6 treatments in low-income countries. But enthusiasm for applying LD-RT for the treatment of COVID-19 patients has been muted yet.

CONCLUSION

In this review, we take a look at LD-RT mechanisms of action in the treatment of nonmalignant diseases, and then through studying both the dark and bright sides of this approach, we provide a thorough discussion if LD-RT might be a promising therapeutic approach in COVID-19 patients.