Introduction

Undergoing cancer therapy introduces many new terms and words to a person’s vocabulary, and it can be very difficult to understand everything that is happening. Radiation pneumonitis is a side effect of some cancer therapies, and you may have been told that you have it or that you are at risk of developing it. Please read on if you would like some more information about radiation pneumonitis. 

Radiation pneumonitis is defined as inflammation affecting the lungs after receiving radiotherapy. This inflammation doesn’t appear instantly after completing a course of radiotherapy and usually develops within a few weeks to up to six months after treatment.^1,2 Radiation pneumonitis is an important potential side effect of radiotherapy as it can make you extremely unwell, and if left untreated, it can develop into lung fibrosis.¹

Causes and risk factors

As the name suggests, radiation pneumonitis is caused by radiotherapy treatment directed at the chest and lungs. The risk of radiation pneumonitis is increased by higher intensity radiation treatment and treatment to larger areas of the lung.³ Lung radiation happens in the following cancers, and so these are the cancers commonly associated with radiation pneumonitis;⁴

• Lung
• Breast
• Oesophageal 
• Lymphoma 
• Thymus

This does not mean that everyone with these cancers will get radiation pneumonitis, and steps are taken to minimise the risk as much as possible during radiotherapy. 

Patient specific factors

In addition to the risks surrounding radiotherapy to the lungs and chest, there are some other risk factors that may increase your chance of developing radiation pneumonitis;^3,4,5

• Increased sensitivity to radiation - caused by having treatment in combination with either chemotherapy or immunotherapy 
• Treatment requiring higher doses of radiation or needing radiotherapy for an increased timeframe 
• Having a lung condition prior to treatment, particularly chronic obstructive pulmonary disease (COPD) 
• Aged 65 or over 
• Treatment for tumours in the mid to lower lung 

Mechanism of action

Radiotherapy is a common cancer treatment that uses radiation to kill cancer cells or damage their DNA through a number of different cellular responses, making it harder for them to replicate.⁶ Cancer cells are particularly sensitive to radiotherapy because they are changing and multiplying quickly,⁶ however, non-cancerous cells can also be affected by radiation.

In radiation pneumonitis, the non-cancerous cells affected are the cells that line the alveoli, which are the tiny bag-like structures found at the ends of the tiniest airways in the lungs, known as the bronchioles. The alveoli are essential parts of the lungs. They are where the oxygen we breathe in is transferred to the bloodstream and carbon dioxide is exchanged to be breathed out.⁷

Following radiotherapy, a large number of cells from the immune system can migrate to the alveoli, causing them to swell.⁵ Additionally, radiotherapy can kill the alveolar cells, as they would with cancerous cells.⁵ In combination these factors reduce the normal ability of the alveoli to transfer oxygen and carbon dioxide correctly, making the lungs in general less effective at their job.⁵

Although radiation pneumonitis can appear up to six months post-radiotherapy, some of the alveolar cell changes can happen much sooner, even within a couple of days of treatment.⁵

Without prompt treatment, there is an increased risk of developing lung fibrosis as a consequence of radiation pneumonitis. This is characterised by changes in the types of cells found in the alveolar cells following long-term inflammation,⁵ making them more stiff.

Clinical signs and symptoms 

Symptoms of radiation pneumonitis may include;^2,3,5

• Shortness of breath 
• Dry cough 
• Fever 
• Chest pain 

These symptoms can worsen as the condition progresses, especially when feeling short of breath, so it is essential to seek medical treatment as soon as possible.⁵

Other marked signs, symptoms and complications that may appear as radiation pneumonitis progresses include;⁵

• Coughing up blood 
• Developing chest infections
• Pleural effusion - where fluid accumulates in the tissue around the lung 
• Pneumothorax - where air escapes into the chest, causing the lung to collapse

Diagnosis

Medical history 

If radiation pneumonitis is suspected, a healthcare professional will take a full history of the symptoms you have been experiencing, any medical conditions you may have (particularly lung conditions), and the medication you are taking. As radiation pneumonitis is related to radiotherapy treatment, you will be asked about the radiotherapy and chemotherapy you have received.¹ You may also be asked about your history of smoking, as this may be relevant to lung conditions that cause the same symptoms, other than radiation pneumonitis.

Physical examination

Once a medical history has been taken, a healthcare professional will carry out a physical examination. This may differ slightly depending on the symptoms you are experiencing, however checking your ‘vital’ signs, such as heart rate, blood pressure, temperature and the amount of oxygen in your blood will happen routinely.¹ A healthcare professional will also listen to various points on your chest to ascertain whether any unusual sounds can be heard when you breathe in and out.¹ Blood tests may also be taken to check for signs of inflammation and infection.¹

Medical imaging

The first signs of radiation pneumonitis can be seen using medical imaging and can appear before physical symptoms are noticed.⁵ An x-ray or CT scan may be able to show whether the lungs have changed in size, or are showing signs of changes at the bronchioles.⁵ Radiation pneumonitis can look like many other lung conditions on medical images, and so this information is used in combination with the clinical history, physical examination and other tests.⁵

Lung function tests

Lung function tests may also be described as pulmonary function tests and can include spirometry. This test looks at how well the lungs are able to expand when breathing in, and how responsive they are during the different stages of breathing. Similar to medical imaging findings, lung function tests can point towards radiation pneumonitis before any symptoms are even noticed.⁵

Differential diagnosis 

The symptoms, medical imaging and lung function test findings of radiation pneumonitis can all be found in other lung conditions. Your healthcare professional will want to rule out the following conditions as being a possible cause of your symptoms;⁸

• COPD 
• Pneumonia 
• Pneumonitis caused by medications, and not radiation 
• Pulmonary embolism 
• Lung changes caused by heart failure 

The key difference between radiation pneumonitis and these conditions is recent exposure to radiotherapy, with or without chemotherapy - however, not all cases will automatically be radiation pneumonitis and may need different management plans.

Management

The treatment required for radiation pneumonitis will depend on how the symptoms affect your quality of life, with consideration for how the lungs appear on medical imaging,⁵ alongside other investigations Initial treatment is usually conservative, with a focus on relieving symptoms. This can include the use of oxygen and medication to relieve symptoms. With very mild cases you may need no treatment at all.⁴ 

Conservative treatment

Conservative management of radiation pneumonitis will often include basic methods to help your lungs function in the best way possible whilst you are unwell. They include;³

• Resting if you start to feel short of breath
• Sleeping in a more upright position at night 
• Being mindful of very hot or very cold days, as this can make it feel harder to breathe well

Medication 

Medication may be needed if your symptoms cannot be managed with the methods above alone, and include the following;^1,5,9

• Steroid treatment to help reduce inflammation 
• Antibiotics to treat any infections contributing to the symptoms 
• Medication to reduce or prevent fibrosis of the lungs 
• Bronchodilating medication to help open up the airways

Supportive care in severe illness 

In cases of radiation pneumonitis where a patient is severely unwell, they may need to be admitted into the hospital for management with inhaled oxygen and intravenous medications.^1,5 Some people may also need their further support with their breathing This can involve intubation and ventilation in the most severe cases, where breathing is managed via a machine.¹

Prevention

Certain measures can be taken during treatment with radiotherapy to reduce the risk of developing radiation pneumonitis. This is managed in part through planning radiotherapy such that it targets as little of the healthy lung tissue as possible, thereby reducing the area exposed to radiation.² Considerations are also made regarding patient characteristics that can increase the risk of developing radiation pneumonitis, and this is taken into account before starting radiotherapy.¹⁰ 

Prognosis

The prognosis for radiation pneumonitis is best when managed at an early stage of the condition, and so any symptoms that are suspicious should be reported urgently to a healthcare professional.¹⁰ With prompt treatment, radiation pneumonitis can fully resolve.⁸

If left untreated, radiation pneumonitis can develop into lung fibrosis.⁵

Research and developments

Studies are being carried out to assess whether a medicine called Nintedanib, which is already used to treat lung fibrosis, may also be suitable to manage radiation pneumonitis.¹¹ Nintedanib is a form of immunotherapy, where the medication can support a person’s immune system's fight against the changes caused by radiation pneumonitis.¹²

Summary

Cancer therapy can be very complex, introducing the patient to both new medications and symptoms resulting from treatments for the original condition. Radiation pneumonitis is one such additional condition, characterised by lung inflammation that appears within weeks to several months after radiotherapy. Left untreated, radiation pneumonitis can result in irreversible lung damage through lung fibrosis, so early detection and intervention are essential.

Radiation pneumonitis can be a risk of any radiotherapy directed at the chest area, so ensuring that radiation is given at the right dose, for the right amount of time in a specific area of the chest is important in reducing the risk. Factors specific to the patient, such as age and previous lung issues can also increase the risk of developing radiation pneumonitis. Your health professional will be able to discuss this risk with you. 

Symptoms of radiation pneumonitis include shortness of breath, a dry cough and fever. Left untreated, this can progress to chest pain, fluid accumulating around the lung, or even a collapsed lung. 

Radiation pneumonitis can appear to be very similar to other lung conditions before diagnosis, so it is important to exclude any other potential causes, as their treatment will be different. Your healthcare professional will take a medical history, carry out a physical examination, and may request medical imaging and lung function tests

Treatment for radiation pneumonitis varies depending on the severity of symptoms but can include practical measures such as getting enough rest, medication and oxygen therapy, and hospitalisation in the most extreme cases. As with many conditions, early detection and treatment are essential in order to minimise the effects of radiation pneumonitis. The role of novel treatments such as immunotherapy in the management of radiation pneumonitis is being researched.