At time of lung cancer diagnosis, the median NfL level was comparable between the stage I patients and the 16 stage IV patients without brain metastasis at diagnosis 16 pg/mL (range: 8–165; interquartile range (IQR): 13–25) vs. 20 pg/mL (range: 6–54; IQR: 13–32; p = 0.702, Figure 1), indicating that stage of disease has no influence on the NfL level. Here, NEFL is linked to lung cancer.