Pulmonary Complications of Anticancer Treatment
Summary of Key Points
Radiation-Induced Lung Injury (Radiation Pneumonitis and/or Fibrosis)
Risk Factors
• Risk factors include radiation dose and volume of lung irradiated, which may be expressed as mean lung dose or as the Vx, that is, the percentage of normal lung tissue irradiated to a dose above a certain threshold dose.
• Older age, co-morbidities (including chronic obstructive pulmonary disease), and/or low performance status are risk factors.
• The location of the tumor is a risk factor; irradiation of lower lobe primary lung tumors may carry a higher risk than irradiation of other tumors, although this may reflect the higher volume irradiated with lower lobe tumors.
• Biological factors can carry risk, including levels of circulating cytokines such as transforming growth factor–β and interleukin-6.
Diagnosis
• The predominant symptoms are dyspnea and hypoxia, especially upon exertion.
• Fever (usually low grade if present at all), cough, pleuritic chest pain, and other pulmonary symptoms also frequently occur.
• Diffusing capacity of the lung for carbon dioxide is the most sensitive pulmonary function.
• Interstitial or ground-glass infiltrate usually corresponds to the irradiated volume.
• Findings at bronchoscopy are unremarkable (bronchial lavage may reveal lymphocytosis).
• Pulmonary embolism, infection, and progressive tumor must be ruled out. These conditions can co-exist with radiation pneumonitis.
Treatment
• Prevention is far more important than treatment. Patients must be selected carefully for thoracic radiation, and irradiated volumes must be limited.
• Corticosteroids are very useful in the management of acute and subacute pneumonitis (although they have no prophylactic or therapeutic value in the management of long-term radiation fibrosis).
• A pulmonologist should be consulted for all grade 3 cases and most grade 2 cases.
• Oxygen should be administered as indicated to prevent hypoxia.
• High doses of corticosteroids (60 mg/day of prednisone) should be administered with slow tapering (over several weeks to months) for severe grade 2 or any grade 3 radiation pneumonitis.
• If prolonged corticosteroid treatment is anticipated, prophylaxis against corticosteroid complications is needed, including gastrointestinal, infectious, and osteoporosis prophylaxis and dietary and pharmacologic management of hyperglycemia.
• Antibiotics, bronchodilators, diuretics, and anticoagulation should be used as indicated for co-existing cardiopulmonary illnesses.
