Clinical significance of serum pulmonary surfactant proteins A and D for the early detection of radiation pneumonitis

Abstract

Purpose: Radiation pneumonitis (RP) is one of the most serious complications for patients who receive thoracic irradiation. To avoid this, early diagnosis of radiation pneumonitis is extremely important. The purpose of the present study is to investigate whether serum pulmonary surfactant proteins A and D (SP-A and SP-D, respectively) could be useful markers for RP. Methods and Materials: Eighty-six patients (lung cancer: 42 [primary: 39, metastatic: 3], breast cancer: 23, esophageal cancer: 21) who underwent radiation therapy were prospectively studied. Radiation doses ranged from 30–76 Gy (median, 58 Gy). Serum SP-A and SP-D levels were evaluated sequentially by a sandwich enzyme-linked immunosorbent assay (ELISA) method before, during, and throughout the follow-up period until the development of symptomatic RP or until one year after completion of radiotherapy. Specificity of the ELISA results was confirmed by Western blot analysis. Patients symptomatic for RP were graded according to the Common Toxicity Criteria. Results: RP occurred in 19 patients. Serum SP-D levels of patients with RP were sequentially higher than those in patients without RP. In the monitoring, serum SP-D levels at 50–60 Gy showed greater sensitivity and positive predictive values for RP detection (74% and 68%, respectively) than SP-A (26% and 21%, respectively). Western blot analysis showed that the development of RP was due to overproduction, but not proteolysis of surfactant proteins. Conclusion: We confirm that serum SP-A and SP-D monitoring is a practical and useful diagnostic method for the early detection of RP.