A 65-year-old woman with T2a N2 M0 squamous cell lung cancer of the left upper lobe presents to the emergency department. She has a two-week history of progressively worsening shortness of breath on exertion, and a dry cough. She completed four weeks of radical radiotherapy two months ago.
What is radiation pneumonitis?
What are the risk factors for the formation of radiation pneumonitis?
How should a patient with radiation pneumonitis be managed?
What is radiation pneumonitis?
Radiation-related lung toxicity is divided into early and late phases. Early-phase toxicity is defined as radiation pneumonitis. Late-phase toxicity is defined as radiation-related pulmonary fibrosis.
Radiation pneumonitis usually develops two to three months after the completion of radiotherapy, but it can on occasions develop within the first month after radiotherapy, or up to six months after radiotherapy.1 From 5% to 15% of patients who receive external beam radiotherapy for lung cancer will develop symptomatic radiation pneumonitis, and up to 10% of patients receiving adjuvant radiotherapy for breast cancer will be symptomatic. A larger percentage of patients will have radiological features of pneumonitis but will be asymptomatic.1
Ionizing radiation leads to direct cellular damage to normal lung tissue; it also causes upregulation of cytokines that mediate the inflammatory process that leads to pneumonitis.
Radiotherapy can damage epithelial and endothelial cells, which causes narrowing of the pulmonary vasculature and small vessel thrombosis. An inflammatory exudate is formed that leads to alveolar cell hyperplasia.
Shortness of breath is the commonest symptom present, and the severity can vary. Cough is less common and is usually non-productive. Occasionally there can also be low-grade fever.2 In rare cases there are fine crackles and friction rubs on auscultation. However, quite often there are no clinical signs.
Radiation pneumonitis does not necessarily have to show any radiological features on chest X-ray. If any are present there can be localized interstitial shadowing visible, normally corresponding to the treatment field. Computed tomography (CT) scans of thorax will typically show ground glass attenuation within the area of irradiation. A symptom severity scoring system is shown in Table 26.1
Table 26.1Radiation Therapy Oncology Group (RTOG) grading of radiation lung toxicity based on symptoms |Favorite Table|Download (.pdf) Table 26.1 Radiation Therapy Oncology Group (RTOG) grading of radiation lung toxicity based on symptoms
|Grade 1 ||Mild cough or mild shortness of breath on exertion; no clinical intervention required |
|Grade 2 ||Cough requiring narcotic-based antitussive (codeine linctus) |
|Grade 3 ||Severe cough not responsive to narcotic or shortness of breath at rest; requires ambulatory oxygen or corticosteroids |
|Grade 4 ||Continuous oxygen or assisted ventilation required |
|Grade 5 ||Fatal |
What are the risk factors for the development of radiation pneumonitis?