Values of serum MMP-9 and SAA in prediction of severe radiation pneumonitis complicated with pulmonary infection in NSCLC patients after chest radiotherapy

OBJECTIVE To explore the values of serum matrix metalloproteinase-9 (MMP-9) and serum amyloid protein A (SAA) in prediction of severe radiation pneumonitis (SRP) complicated with pulmonary infection in patients with non-small cell lung cancer (NSCLC) patients after chest radiotherapy. METHODS From Jun 2019 to Jan 2022, totally 86 locally advanced NSCLC patients who had SRP in Tianjin Fifth Central Hospital after chest radiotherapy were recruited as the research subjects and were divided into the pulmonary infection group with 20 cases and the non-pulmonary infection group with 66 cases according to the status of complication with pulmonary infection. The levels of serum MMP-9 and SAA were respectively detected before and after the radiotherapy. The values of the serum MMP-9 and SAA in prediction of SRP complicated with pulmonary infection were evaluated by means of receiver operating characteristic (ROC) curves. RESULTS There were no significant differences in the serum MMP-9, SAA and lung function indexes between the two groups of patients 1 day before the radiotherapy; The levels of serum MMP-9 and SAA of the pulmonary infection group were significantly higher than those of the non-pulmonary infection group after the radiotherapy for 1 month, however, the forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) of the pulmonary infection group were significantly lower than those of the non-pulmonary infection group (P＜0.05). The sensitivity, specificity and area under ROC curve (AUC) of the joint detection of serum MMP-9 and SAA were significantly greater in prediction of pulmonary infection in the SRP patients than those of the single detection of the two indexes (P＜0.05). CONCLUSION The serum MMP-9 and SAA can be used as indicators for the risk of pulmonary infection in the SRP patients, which may facilitate the assessment of prognosis of the patients. The joint detection of the two indexes can serve as reliable indexes for prediction of pulmonary infection in the SRP patients.