For patients undergoing radical radiotherapy, the highly enriched pathways in cluster 2 were extracellular matrix (ECM) receptor interaction, cell cycle, TGF beta signaling pathway, antigen processing and presentation, Toll like receptor signaling pathway, complement and coagulation cascades, Wnt signaling pathway, chronic myeloid leukemia, lysosome, Notch signaling pathway, circadian rhythm mammal, Fc gamma R-mediated phagocytosis, colorectal cancer, P53 signaling pathway, focal adhesion, apoptosis, small cell lung cancer, neurotrophin signaling pathway, and pancreatic cancer (Figure 4E). The gene discussed is BDNF; the disease is small cell lung carcinoma.