High SOD and low GPX activities in RBC predict susceptibility of lung cancer patients to radiation pneumonitis

摘要

Radiation pneumonitis is an unpredictable complication of radiotherapy for lung cancer and a condition which can cause significant morbidity. The ability to identify patients at a high risk of developing pneumonitis is critical, since it will enable the individualization of the treatment plan. Because the cytotoxic effect of radiation is propagated through ROS and ROS-driven oxidative stress, the role of anti-oxidant defense systems in radiation pneumonitis was investigated. Using the pneumonitis-sensitive C3H/HeN mice as a model, we demonstrated that the anti-oxidant response of the lung correlated well with that of RBC. We then proceeded to test whether differences of RBC anti-oxidant response would predict the pneumonitis development in patients. SOD, GPX, CAT activities and glutathione in RBC were measured at baseline and then weekly for 6 weeks of treatment in fifteen eligible patients receiving concurrent chemo-radiotherapy for unresectable stage III NSCLC. Striking differences were found in the anti-oxidant activities of RBC with respect to the pneumonitis development. Those who developed pneumonitis showed higher SOD and lower GPX activities at baseline compared to those who did not (3.7 vs. 6.8 unit/mg for median SOD, 16.5 vs. 10.7 nmol/min/mg for median GPX). The functional imbalance of SOD and GPX was displayed consistently throughout the treatment period. The sensitivity and specificity of pneumonitis prediction were further increased when the GPX/SOD ratio was analyzed (pre-treatment P = 0.0046). Our results provide a strong rationale to monitor SOD and GPX activities of RBC to identify patients who are at risk of developing pneumonitis, and to implement a strategy of increasing the GPX/SOD ratio in order to lower the risk.