radiation pneumonitis
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Introduction
A subacute inflammatory pneumonitis which occurs in response to exposure of the lungs to therapeutic doses of ionizing radiation.
Etiology
- risk factors
- concurrent chemotherapy
- prior radiation therapy
- recent withdrawal of glucocorticoids
Pathology
- radiation initially effects pulmonary capillary endothelial cells & type II pneumocytes
- lymphocytic stimulation can lead to bronchiolitis obliterans with organizing pneumonia (BOOP)
Clinical manifestations
- symptoms generally begin insidiously 1-3 months (4-12 weeks)[3] after completion of radiation
- cough
- dyspnea out of proportion to chest X-ray findings
- low grade fever
- non-specific & variable, depending upon
- total dose of radiation
- fractionation schedule
- volume of lung irradiated
- concomitant administration of cytotoxic agent
- withdrawal of steroids
Laboratory
- arterial blood gas
- impairment of gas exchange in more severe cases
Diagnostic procedures
- pulmonary function testing
- decreased DLCO in more severe cases
Radiology
- chest radiograph:
- new infiltrate corresponding to region of radiation exposure
- non anatomic straight line demarcating involved vs non-involved lung parenchyma is pathognomonic[3]
- CT of thorax
- hazy opacities with ground glass attenuation
- distribution conforms to radiation port rather than anatomical lobes of the lung or bronchopulmonary segments
- air bronchograms with slight dilation of peripheral bronchi
Complications
- abnormalities may resolve within 6 months or progress to pulmonary fibrosis, volume loss & bronchiectasis[3]
Differential diagnosis
- infections
- recurrent tumor
- lymphangitic carcinoma
Management
- mild symptoms
- moderate to severe disease
- glucocorticoids[3]
- start prednisone 60-100 mg/day for 3-5 days
- 20-40 mg prednisone/day for 2-4 weeks
- taper prednisone to none after 4 weeks
- only 50-80% will respond to glucocorticoid therapy[3]
- glucocorticoids[3]
More general terms
Additional terms
References
- ↑ Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 256
- ↑ Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 762
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 17, 18, 19. American College of Physicians, Philadelphia 2009, 2012, 2015, 2018, 2022.