Table 1.

Summary of published preliminary results on the use of low dose radiation therapy (LDRT) in COVID-19

S. no.	Study name (Authors) (Reference)	Study type	Intervention	No. of patients	Results	Conclusions
1	Immunomodulatory Low-Dose Whole-Lung Radiation for Patients with Coronavirus Disease 2019-Related Pneumonia (Hess et al. 2021)	Investigator-initiated, single-institution combined phase 1 and 2 trial for patients with COVID-19 pneumonia	1.5 Gy whole-lung LD-RT, for COVID-19 patients	10	Quicker recovery to room air in LDRT treated COVID patients than age- and comorbidity-matched controls, with trending or significant improvements in delirium, radiographs, and biomarkers, and no significant acute toxicity	Whole lung LDRT appears to be safe and may be an effective immunomodulatory treatment in COVID-19 patients
2	COVID-19 pneumonia treated with ultra-low doses of radiotherapy (ULTRA-COVID study): a single institution report of two cases (Moreno-Olmedo et al. 2021)	Prospective study of Ultra-Low Doses of Radiation Therapy Applied to COVID-19 pneumonia patients who show no improvement with medical therapy and are not candidates for invasive mechanical ventilation	Total single 0.8 Gy dose administered in a 3 min session	2	Significant clinical response with good radiological response was observed in both the cases after single radiotherapy session. Both patients discharged from hospital in less than 2 weeks after radiation treatment	Ultra-LDRT showed potential benefits (preliminary clinical and radiological results) in the treatment of SARS-CoV‑2 pneumonia patients during the acute inflammatory phase
3	Low dose radiation therapy for COVID-19 pneumonia: A pilot study (Sharma et al. 2020)	Pilot study assessing the feasibility and clinical efficacy of LDRT to lungs in patients with COVID-19	LDRT to both lungs with a single dose of 0.7 Gy	10	Nine patients had complete clinical recovery mostly within a period ranging from 3–7 days (90% response rate). 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	LDRT in COVID-19 patients with moderate to severe risk disease is clinically effective
4	Low-Dose Whole-Lung Irradiation for COVID-19 Pneumonia: Final Results of a Pilot Study (Ameri et al. 2021)	Pilot trial evaluating low-dose whole-lung irradiation (LD-WLI) in patients with COVID-19 pneumonia	LD-WLI with a single fraction of 0.5 Gy or 1 Gy 5, 1, and 4 patients received single-dose 0.5 Gy, two-doses 0.5 Gy, and single-dose 1.0 Gy LD-WLI, respectively	10	The median age was 75 years (80% male). Nine patients showed improvement in oxygen saturation by pulse oximetry (SpO2) after 1 day The response rate (RR), clinical recovery (CR), and 28-day mortality of the single 0.5 Gy and 1.0 Gy WLI groups were 71.4% versus 50% (P = .57), 60% versus 50% (P = .64), and 50% versus 75% (P = .57), respectively	Single fraction of 0.5 Gy or 1 Gy LD-WLI in COVID-19 patients is feasible
5	Low-Dose Radiation Therapy in the Management of Coronavirus Disease 2019 (COVID-19) Pneumonia (LOWRAD-Cov19): Preliminary Report (Sanmamed et al. 2021)	Prospective, single-arm, phase 1/2 clinical trial with COVID-19 patients	Patients received a single fraction of 1.0 Gy to whole lungs	9	The median age was 66 years. Statistically significant changes were seen in the extension score (P = .03). SatO2/FiO2 index (SAFI index) significantly improved 72 h and 1 week after LD-RT (P = 0.01). Inflammatory blood parameters decreased 1 week after RT compared with the baseline	LD-RT in COVID-19 pneumonia was feasible and well-tolerated, with potential clinical improvement
6	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) (Arenas et al. 2021)	Multicenter, nonrandomized prospective trial in COVID-19 patients with moderate–severe pneumonia and comorbidities or low performance status making them unfit for admission to the intensive care unit (ICU)	The LDRT plan was individualized and consisted of a single dose of 0.5 Gy, with the possibility of a second dose of 0.5 Gy after 48 h, depending on the response to the first dose	36	The mean age was 84 years. All enrolled patients had comorbidities along with bilateral pulmonary infiltrates on chest X-ray and received dexamethasone treatment. 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 with mean SpO2 pretreatment value of 94.28%. A significant improvement was observed in the percentage of lung involvement in the CT scan at 1 week after LD-RT in those who survived (23/36, 64%). No radiation treatment related adverse effects were reported	LD-RT appeared to be a safe and feasible modality in patients with COVID-19 pneumonia having significant comorbidities
7	Low-Dose Radiation Therapy for Severe COVID-19 Pneumonia: A Randomized Double-Blind Study (Papachristofilou et al. 2021)	Randomized double-blind study in critically ill patients requiring mechanical ventilation for COVID-19 pneumonia	Patients were randomized to 1.0 Gy whole-lung LDRT or sham irradiation (sham-RT)	20	Overall survival at 28 days was identical at 63.6% in both arms (P = 0.69) 15-day ventilator-free days showed no difference 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 Pronounced reduction in lymphocyte counts after LDRT (P < 0.01), but secondary endpoint analyses of secondary showed no significant differences between the groups	Critically ill COVID-19 pneumonia patients that require mechanical ventilation showed no improvement in clinical outcomes when treated with whole lung LDRT