Taken together, several considerations must be made when utilizing blood-based IL11 levels as a biomarker in NSCLC: (1) Not all lung cancer patients have detectable circulating IL11 levels possibly reflecting disease severity, (2) site of assessment appears to be most accurate at the disease source, and (3) concomitant diseases can complicate interpretation of blood IL11 concentrations. The gene discussed is IL11; the disease is lung cancer.