Radiation damage to the lungs following therapy depends on irradiated volume, total dose, number of fractons and adjuvant chemotherapy. Significant damage is unusual at less than 2000 rads over 2-3 weeks and common at greater than 6000 rads given over 5-6 weeks.
Acute radiation pneumonitis occurs at approximately one month after treatment. Pathologically there is sloughing of the alveolar and bronchial cells, exudation and depletion of surfactant. Clinically there is nonproductive cough, SOB, weakness and fever. Radiographically there is initial patchy opacity and atelectasis within the port, persisting up to one month. Complete recovery or progression to death can occur. Steroid therapy is treatment of choice. Chronic radiation damage appears 9-12 months post treatment and results in volume loss, fibrosis (hilar to periphery), pleural thickening and possibly pericardial effusion. Again, the reaction is contained within the radiation portals.