Objective  To investigate the diagnostic value of serum kreb von den lungen-6 (KL-6) in lung injury from postoperative adjuvant treatment in non-small cell lung cancer (NSCLC).

  Methods  This study is a retrospective analysis including NSCLC with postoperative adjuvant treatment and NSCLC with merely surgical treatment patients diagnosed and treated in Shengjing Hospital of China Medical University from November 2017 to July 2020. Consensus on the diagnosis of drug induced lung injury and radiation induced lung injury was used as the diagnostic criteria for lung injury from postoperative adjuvant treatment. NSCLC patients with postoperative adjuvant treatment were divided into the lung-injury group and the non lung-injury group. those only with surgery were as NSCLC-surgery group. Match the healthy adults of the physical examination center at the same period as the healthy control group based on the age and gender. Fasting venous blood was collected from NSCLC patients and healthy adults for detection of serum KL-6. The time of venous blood collection was on the day of lung-injury diagnosis for the lung-injury group, after 3 to 4 months of adjuvant treatment for the non lung-injury group, before and 7 to 10 days after surgery for NSCLC-surgery group, and on the day of physical examination for the healthy control group. The levels of serum KL-6 in each group were compared, and the non lung-injury group was used as the control, the diagnostic threshold value of serum KL-6 for adjuvant therapeutic lung injury was preliminarily established based on the receiver operating characteristic(ROC) curve.

  Results  A total of 206 NSCLC patients who met the selection and exclusion criteria were enrolled, of which 51 cases were in lung-injury group, 52 cases were in non lung-injury group, and 103 cases were in NSCLC-surgery group. Meanwhile, 103 cases in healthy control group were enrolled. There was no significant difference among the basic clinical data of the four groups. The levels of serum KL-6 in the descending order were lung-injury group 512.40 (322.30, 819.20)kU/L, pre-operation of the NSCLC-surgery group 204.40 (162.70, 283.20)kU/L, healthy control group 177.70 (154.20, 206.40)kU/L, non lung-injury group 147.80 (114.25, 229.80)kU/L, and post-operation of the NSCLC-surgery group 143.80 (111.90, 247.80)kU/L. There was no significant difference in serum KL-6 between the non lung-injury group and post-operation of the NSCLC-surgery group (P=0.879), while the difference between other groups were statistically significant (all P < 0.05). The ROC curve analysis showed that the area under the curve (AUC) of serum KL-6 for the diagnosis of lung injury from NSCLC postoperative adjuvant treatment was 0.972 (95% CI: 0.948-0.997), and the diagnostic sensitivity, specificity, the positive and negative likelihood ratio were 86.3% (95% CI: 73.0%-94.1%), 96.2% (95% CI: 86.2%-98.7%), 22.43 (95% CI: 5.74-87.69), 0.14 (95% CI: 0.07-0.28), respectively. The best diagnostic cut-off value was 310.15 kU/L.

  Conclusions  Serum KL-6 is significantly increased in the patients with lung injury from NSCLC postoperative adjuvant treatment, and it has high application value in the diagnosis of lung injury from postoperative adjuvant treatment in NSCLC, but it still needs further verification by prospective studies with large samples.