Purpose: To evaluate the diagnostic potential of bronchoalveolar lavage fluid analysis in radiation-induced lung injury.
Methods and materials: Thirty patients with inoperable non-small cell lung cancer received either high-dose hyperfractionated radiotherapy or radiotherapy and interferon, a potential radiosensitizer, or radiotherapy and N-acetylcysteine, a potential radioprotector. Bronchoalveolar lavages were performed before and immediately after radiotherapy, and thereafter 6-8 weeks and 3 months after radiotherapy. Total and differential cell counts were measured from the bronchoalveolar lavage fluid samples. Urea measured in serum and in bronchoalveolar lavage fluid was used to calculate epithelial lining fluid. The concentrations of protein and phosphatidylcholine, the major surfactant phospholipid, in epithelial lining fluid were measured. The extent of radiation-induced lung injury was assessed from computed tomographies performed before radiotherapy, and 6-8 weeks and 3 months after radiotherapy.
Results: More patients in the interferon-arm developed radiation pneumonitis than did patients in the other groups, but no significant differences in alveolar fluid indices were noted between the groups. When all the patients were studied together, radiation was shown to have induced a significant relative increase of lymphocytes in bronchoalveolar lavage fluid 6-8 weeks and 3 months after the end of radiotherapy. The concentration of phosphatidylcholine in epithelial lining fluid decreased significantly 6-8 weeks and 3 months after treatment. The increase in protein concentration in epithelial lining fluid reached a statistically significant level 6-8 weeks after radiotherapy.
Conclusion: Analysis of bronchoalveolar lavage fluid predicts the degree of radiation pneumonitis; however, radiology remains to be "the gold standard."