As the Coronavirus pandemic continues to affect millions worldwide, scientists have been racing to find treatments to alleviate symptoms in the worst affected patients. Low dose radiation therapy (LDRT), which is commonly used as a cancer treatment, is the latest option being considered. The concept is not new and has already been used to treat pneumonia in the early 20th century, but its use comes with its own risks and complications.

How does Covid-19 cause pneumonia?

While the virus only causes mild symptoms in most cases, in a small number of patients it can overstimulate the body’s immune response. Since Covid-19 is a respiratory disease, it reaches far into the respiratory tract, including the lungs. When the virus comes into contact with mucous membranes in the nose, mouth, and eyes, it multiplies and infects nearby cells. It then travels down the airway, irritating the inner linings. This causes the lungs to swell as they build up with fluid and debris, causing a condition called pneumonia. 

In some cases, the body can overreact to an infection in the lungs, causing so-called “cytokine storms”. Cytokines are small proteins released in the body but having large amounts of them released into the blood can cause further inflammation in the lungs, causing or worsening the pneumonia. Scientists are now looking at whether low dose radiation therapy can help abate such cytokine storms and therefore treat the pneumonia with its anti-inflammatory properties.

What is low dose radiation therapy and how can it treat pneumonia?

Radiation is widely used in medicine to diagnose and treat certain conditions. Radiation therapy is the use of ionizing radiation to control or kill malignant cells. As such, it is one of the main ways to treat cancer today. The radiation works by damaging the DNA of cancerous tissue leading to cellular death. Of course, ionizing radiation can also be dangerous and lead to cancer by causing mutation in nearby healthy cells. Targeted low dose radiation therapy mitigates this risk by reducing the amount of damaging ionizing radiation to surrounding cells.

The concept of using LDRT in the treatment of pneumonia actually isn’t all that new, with initial trials dating back to 1905 at The University of Pennsylvania. It was also used to treat viral pneumonia after the 1918 influenza pandemic. Most reports were written from 1930 to 1946 in a time when advanced intensive care including the use of respirators was not possible. Although these studies produced good results, the use of radiation to treat pneumonia dropped after 1946 due to the emergence of other ways to treat bacterial infections such as antibiotics like penicillin. There have been no further studies into the use of low radiation therapy to treat pneumonia after 1946. This area of research has only recently been revived by our desperate search for a cure during the Covid-19 pandemic, 74 years later.

What have the studies found?

In June of this year, the results from the first trial in humans showed promising results. The small scale pilot study, which was later published in the American Cancer Society Journal, found that “low-dose whole-lung radiation led to rapid improvements” in five oxygen-dependent elderly patients with Covid-19 pneumonia. It also concluded that LDRT appears to be safe and should be studied further.

Another clinical trial conducted in Iran and published in the International Journal of Radiation Oncology also found “encouraging results”. The research concluded LDRT had a response rate of 80% and “starts to demonstrate efficacy from the first day of irradiation”. There are further ongoing trials researching the effectiveness of LDRT in Covid-19 patients, including the VENTED and PREVENT studies at the Ohio State University Comprehensive Cancer Center. 

What are the concerns? 

The main concern regarding the use of LDRT are the unknown long-term effects on the body. While LDRT can sterilize inflammatory lung tissue, it could damage other healthy cells in the lungs. Another practical problem of treating Covid-19 patients in radiotherapy clinics is the potential infection risk to cancer patients, who are extremely vulnerable to the virus. This had led some scientists to argue that the potential risk of exposing patients to radiation in clinical trials outweigh the potential benefits. Nevertheless, we will need to wait for more studies on the effectiveness of LDRT before it becomes a real treatment option for hospitalised Covid-19 patients today. 

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