Low Dose Radiation Therapy for Covid-19 Pneumonia: A Pilot Study

There is no specific antiviral treatment recommended for COVID-19, and no vaccine is currently available. The treatment is symptomatic, and oxygen therapy represents the major treatment intervention for patients with severe infection. Mechanical ventilation may be necessary in cases of respiratory failure refractory to oxygen therapy, whereas hemodynamic support is essential for managing septic shock. The death rate ranges from 2-15% in different group of patients.

COVID-19 pandemic is unprecedented in modern history of humankind and it has become imperative to find novel treatments to mitigate the casualties caused by infection. The clinical spectrum of COVID-19 varies from mild symptoms to critical conditions requiring ventilatory support and ICU care. According to Chinese CDC report, 81% patients had mild disease (non-pneumonia and mild pneumonia), 14% had severe disease and 5% had critical disease. Based on severity of symptoms, there are several scoring methods which can predict the outcome of disease. National early warning score (NEWS) is a popular scoring system used for non-ICU patients suffering from acute illness. This score helps in quickly determining the degree of illness and intervention required. It also provides likelihood of death or admission to an ICU. Based on this score any illness can be categorized as mild (Score <4), moderate (Score 5-6 or individual 3) and severe (Score ≥7). According to this scoring system, Covid-19 patients having a score of 5-6 will have probability of 15.7% critical events (HDU/ICU admission or 30-day mortality) and those having score ≥7 will have about 24.1% critical events.

The pathogenesis of COVID-19 pneumonitis appears to involve a cytokine storm with elevated pro- inflammatory cytokines such as IL-6 and TNFα among many others, leading to an onslaught of neutrophils and macrophages, diffuse alveolar damage and respiratory failure. This is where a potential opportunity for low-dose radiation therapy (LDRT) emerges. LDRT is a potential treatment for COVID-19 pneumonia since it has an anti-inflammatory action. Successful management of worsening pneumonia will reduce the development of ARDS and thereby preventing deaths.

Availability of megavoltage beam in modern times has improved our dosimetry in treating deep targets. Radiotherapy which can penetrate lobar and interstitial space can help in preventing both lobar as well as interstitial pneumonia. In the absence of any effective drug and, historical data suggests that low dose of 0.5 to 1 Gy radiotherapy to whole lung can possibly prevent cytokine storm and critical events (ICU admission, mechanical ventilation or death).

The initial use of X-rays to treat patients with pneumonia was reported in 1907. This report offered a new mechanistic insight founded on the dose response, proposing that low doses of X-rays would affect disease resolution. It was observed that not only did the X-ray treatment has lifesaving potential, but it was also effective when other treatments had reached their therapeutic limits as seen in cases of chronic bronchopneumonia, which could be resolved with a single administration of X-rays. Subsequent reports suggested that LDRT was successful in decreasing the mortality rate in untreated patients from about 30% to 5-10%.