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

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.

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 Irradiation as a Novel treatment for COVID-19: Final Results of the Prospective Randomized trial (WINCOVID trial)

Background and purpose

The ability of low dose radiotherapy (LDRT) to control the unprecedented cytokine release associated with COVID-19 pathogenesis has been an area of widespread research since the COVID pandemic. It has not been studied adequately whether the anti-inflammatory effect of LDRT provides additional benefit when used concurrently with steroids amongst other standard pharmacologic therapy.

Material and methods

51 RT-PCR positive COVID-19 patients were recruited between November 2020 and July 2021. 34 patients were allotted to receive 0.5 Gy single session LDRT along with standard pharmacologic therapy while 17 patients received standard pharmacologic therapy alone. All had SpO₂ <94% on room air, respiratory frequency >24/min and SpO₂/FiO₂ (SF) ratio between >89 but <357. All patients underwent a baseline CT scan. They were followed up for 28 days during when serial SF ratio, blood biomarkers (CRP, Serum ferritin, IL-6), Absolute lymphocyte count (ALC), repeat CT scan were performed at pre-defined time points.

Results

LDRT showed a statistically significant early improvement in oxygenation, an early time to clinical recovery, early hospital discharge and better radiological resolution compared to control group. There was no statistically significant difference between the two groups with respect to ALC or blood biomarkers at any of the measured time points. The 28-day mortality rate did not show statistically significant difference between the two groups.

Conclusion

LDRT can be considered for selected oxygen-dependent moderate to severe COVID-19 patients for rapid relief of respiratory distress. It can be safely combined with standard pharmacologic treatment in such patients for added clinical benefit.

Low-dose radiation therapy (LDRT) for COVID-19 and its deadlier variants

Coronavirus variants are gaining strongholds throughout the globe. Despite early signals that SARS-CoV-2 coronavirus case numbers are easing up in the United States and during the middle of a (not so easy) vaccination roll out, the country has passed a grim landmark of 600,000 deaths. We contend that these numbers would have been much lower if the medical community undertook serious investigations into the potential of low doses of radiation (LDRT) as a mainstream treatment modality for COVID-19 pneumonia. LDRT has been posited to manifest anti-infectious and anti-inflammatory properties at doses of 0.3-1.0 Gy via the activation of the Nrf-2 pathway. Although some researchers are conducting well-designed clinical trials on the potential of LDRT, the deep-rooted, blind, and flawed acceptance of the Linear No-Threshold (LNT) model for ionizing radiation has led to sidelining of this promising therapy and thus unimaginable numbers of deaths in the United States.

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.

Low dose lung radiotherapy for COVID-19 pneumonia: A potential treatment

The covid-19 pandemic has been affecting many countries across the world and lost precious lives. Most patients suffer from respiratory disease which progresses to the severe acute respiratory syndrome, termed as SARS-CoV-2 pneumonia. A systemic inflammatory response occurs in SARS-CoV-2 pneumonia severely ill patients, The inflammation process if uncontrolled has a detrimental effect, and the release of cytokines play an important role leading to lung fibrosis. Radiation therapy used in low doses has an anti-inflammatory and immunomodulatory effect. Its low cost, wider availability, and decreased risk of acute side effects can reduce the burden on the health care system.