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Radiation induced lung disease

Dr Yuranga Weerakkody and Dr Frank Gaillard et al.

Radiation-induced lung disease (RILD) is a frequent complication of radiotherapy to the chest for chest wall or intrathoracic malignancies and can have a variety of appearances, especially depending on when the patient is imaged. Acute and late phases are described, corresponding to radiation pneumonitis and radiation fibrosis respectively. These occur at different times after completion of radiotherapy and have different imaging features and differential diagnoses.

As such they are discussed separately :

The remainder of this article is a general discussion of the effects of radiation on the lung.

Epidemiology

The demographics of patients affected by radiation induced lung disease are those of the underlying condition for which radiation therapy was performed. Typically patients have received radiation therapy for one of the following :

The risk of developing radiation induced lung disease depends on a number of factors including:

  • total dose administered
    • rare below 20Gy
    • almost invariable above 40Gy
  • degree of fractionation
  • prior chemotherapy
    • actinomycin D
    • adriamycin
    • bleomycin
    • busulfan

Clinical presentation

Radiation-induced lung disease has two phases, acute and late. The acute phase typically occurs between 4 and 12 weeks following completion of radiotherapy course, although it may be seen as early as 1 week, especially in patients receiving high total dose and/or also having received chemotherapy 1-3. The late phase usually is seen between 6 and 12 months but can progress for up to 2 years 1,3.

Pathology

The lungs are the most sensitive organ when irradiating the chest, and are the major dose-limiting factor 3.

For discussion of pathology during the acute and late phase, please refer to:

Radiographic features

Radiographic appearances depend on whether the patient is imaged during early or late phase. During the acute phase features are predominantly those of an inflammatory process, whereas in the late phase fibrosis predominates 1.

For discussion of these features please refer to:

Treatment and prognosis

Steroid can reduce the severity of acute radiation pneumonitis 1.

Differential diagnosis

The differential of radiation induced lung disease (RILD) depends on phase of the disease however in both instances differentiation of RILD from infection or tumour recurrence may be difficult.

For discussion of differential diagnoses of acute and late phase changes please refer to:

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