Evaluation of serum KL-6 as a predictive marker of radiation pneumonitis in patients with breast-conservation therapy

Background. Although radiation pneumonitis in radiotherapy following breast-conservation surgery is rare, it may lead to severe pneumonitis as well as to other types of pulmonary dysfunction. This study examined the usefulness of the serum KL-6 level as a new marker for the early detection of radiation pneumonitis. Methods. Twenty-nine consenting patients served as subjects (age range, 32-78 years; mean age, 51 years) between 2001 and 2002. A total tangential irradiation dose of 50 Gy/ 25 fractions (fr) was administered for 5 weeks, using a 4-MV X-ray, and an additional 10 Gy/5 fr for 1 week of 6-MeV electron-beam irradiation was performed for patients with pathological tumor cell findings in the excised tumor margins. Levels of serum KL-6 were measured before and after radiotherapy. Results. Four patients developed radiation pneumonitis, all of whom had elevated post-therapy KL-6 levels. Patients with lower or unchanged KL-6 levels did not develop radiation pneumonitis. There was a significant difference in serum KL-6 levels between patients with and without radiation pneumonitis (P = 0.0421). KL-6 levels remained below the threshold value of 465 U/ml in all patients. Conclusion. For the early detection of radiation pneumonitis following breast-conservation surgery, and to assess the efficacy of therapy, the monitoring and measuring of changes in KL-6 levels before and after radiotherapy is more important than comparing KL-6 levels against the threshold value. Measuring KL-6 serum levels is also useful in assessing the efficacy of therapy for radiation pneumonitis.