Radiation-induced myeloid cell infiltration can be inhibited by targeting the hypoxia-inducible factor-1 alpha/stromal cell-derived factor-1/C-X-C chemokine receptor type 4 (HIF-1α/SDF-1/CXCR4) or colony-stimulating factor 1/colony-stimulating factor 1 receptor (CSF1/CSF1R) pathways, leading to tumor radiosensitization. The gene discussed is CXCR4; the disease is neoplasm.