Radiation lung injury is a common complication of radiation therapy to the thorax. Approximately 43% of all patients undergoing thoracic radiation therapy will develop radiographic change consistent with radiation pneumonitis. However, only 8% of patients undergoing thoracic radiation develop symptoms along with a radiographic change.
There are two well-recognized syndromes of radiation induced lung injury. The first is radiation pneumonitis. There is a latent period of 1-3 months following radiation therapy. Symptoms of dyspnea, cough, fever, or weakness may develop prior to any chest x-ray changes. Chest x-ray findings that are typical include a diffuse haziness around the hila, indistinct pulmonary vessels, and an infiltrate that does not follow anatomic boundaries of the lung.
The second syndrome is that of radiation fibrosis. This is permanent damage that takes 6-24 months to evolve after radiation treatment. Patients may present with dyspnea, cor pulmonale, or chronic cough. Chest x-ray findings include honeycombing and volume loss.
Risk factors for radiation damage to the lung include a radiation dose above 3500 cGy, prior radiation therapy, chemotherapy, steroid treatment withdrawal and pre-existing lung disease. We have found that Prednisone therapy in a dose of 60-100 mg by mouth per day, tapered over several weeks provides significant relief of symptoms to most patients. Patients with concomitant exposure to Bleomycin or Adriamycin represent a subset of patients that in our experience does poorly.