CXCR4 and small cell lung carcinoma: In addition to ligands for SSTR, a number of other molecular imaging probes are in development, such as radiolabeled agonists interacting with the chemokine-receptor CXCR4, which is frequently overexpressed in proliferating SCLC tumors, and seems to be a promising new target for both diagnostic and therapeutic interventions [90,99].