Radiation-induced lung disease
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.
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:
- lung cancer
- breast cancer
- mediastinal malignancies
- lower neck nodal disease
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
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 a 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.
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 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.
The differential of RILD depends on the phase of 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:
- 1. Choi YW, Munden RF, Erasmus JJ et-al. Effects of radiation therapy on the lung: radiologic appearances and differential diagnosis. Radiographics. 24 (4): 985-97. doi:10.1148/rg.244035160 - Pubmed citation
- 2. Ikezoe J, Takashima S, Morimoto S et-al. CT appearance of acute radiation-induced injury in the lung. AJR Am J Roentgenol. 1988;150 (4): 765-70. AJR Am J Roentgenol (abstract) - Pubmed citation
- 3. Collins J, Stern EJ. Chest radiology, the essentials. Lippincott Williams & Wilkins. (2007) ISBN:0781763142. Read it at Google Books - Find it at Amazon
- 4. Roychoudhuri R, Evans H, Robinson D, Møller H. Radiation-induced malignancies following radiotherapy for breast cancer. British journal of cancer. 91 (5): 868-72. doi:10.1038/sj.bjc.6602084 - Pubmed