The association between the serum kl-6 level and the risk of radiation pneumonitis

Background. Radiation pneumonitis is known to be a major adverse event of radiation therapy for locally advanced lung cancer. We conducted a retrospective study to analyze the association between the serum KL-6 level and the risk of radiation pneumonitis. Methods. We reviewed cases of lung cancer treated with chest radiotherapy, excluding stereotactic radiotherapy, between 2004 and 2015. Patients were divided into 2 groups based on a serum KL-6 level of 500 U/ml. Preexisting fibrosis of the lung was evaluated by chest X-ray and computed tomography. Results. In total, 69 patients with lung cancer were evaluated. In the univariate analysis of the patients with fibrosis of the lung, those with an elevated serum KL-6 level showed a higher frequency of radiation pneumonitis than those with a lower level, although no such association was detected among the patients without fibrosis (P = 0.029, Fishers exact test). In the multivariate analysis that included fibrosis of the lung, V20, and the serum KL-6 level as independent variables, the odds ratio (95% confidential interval) for the onset of radiation pneumonitis of KL-6 (per 100 U/ml increase) was 1.0 (0.7-1.2). Conclusion. These findings suggest that an elevated serum KL-6 level is associated with radiation pneumonitis in patients with fibrosis of the lung.