Low dose radiation therapy for COVID-19 pneumonia: brief review of the evidence
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LETTER
Low dose radiation therapy for COVID‑19 pneumonia: brief review of the evidence Peter E. Metcalfe1 Received: 26 June 2020 / Accepted: 30 July 2020 © Australasian College of Physical Scientists and Engineers in Medicine 2020
Introduction During this COVID-19 pandemic prevention of the virus with a vaccine has not yet been successful. Treatment of those patients with the life threatening illness COVID-19 pneumonia is a priority to reduce mortality which in the world setting sits at about 5% of reported cases. Fortunately in Australia, the mortality is currently about 1% of reported cases. Most treatment options focus on existing drugs, some with positive early trial results such as the anti-inflammatory drug dexamethasone which shows a modest overall improvement in survival for non-invasive ventilated patients but a potential one third improvement in survival for patients receiving invasive mechanical ventilation (mortality 29.0% treated vs 40.7% control) [1]. This letter focuses on a novel approach to the treatment of COVID-19 pneumonia using a low dose of external beam radiation x-rays. So named “Low Dose Radiation Therapy” (LDRT). There are multiple historical cohort studies mostly dating from the 1930s that report the administration of one low dose fraction of x-rays (usually less than 0.5 Gy) to treat viral and bacterial pneumonia. Recent publications have suggested that a similar approach could be attempted in clinical trials involving pneumonia resistant COVID-19 patients as a treatment that may improve outcomes. In-fact a small clinical trial has started with 4 out of 5 patients treated with 1.5 Gy LDRT surviving [2]. This letter summarises key historical cohort data and discusses the level of evidence it provides as well as publications that point to the anti-inflammatory potential of doses of LDRT. The two most recent letters that have been published on this subject are by Kirkby and Mackenzie in Radiotherapy and Oncology [3] and Doss in Physics in Medicine & * Peter E. Metcalfe [email protected] 1
Centre for Medical Radiation Physics and School of Physics, University of Wollongong, Wollongong, NSW, Australia
Biology [4]. There is also a very recent point/counterpoint published in medical physics on this subject [5]. While these papers provide several historical references to the cohort data they do not provide explicit detail of some of the compelling evidence provided by these historical publications.
Historical evidence The key comprehensive review paper summarising historical cohort results was written by Calabrese et al. [6]. Note this was published in 2013, which predates the COVID-19 pandemic by seven years! They summarise results of 15 historical studies of treating non-responsive pneumonia with radiation from 1905 onward. Most reports are from 1930 to 1946. Dose levels ranged from 0.3 to 0.5 Gy. In summary, the 15 case reports outlined found 863 cases treated and 717 cases cured (17% not cured). The largest reported cohort was that of Powell [7] who reported 231 cases treated and
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