Here, we address the extent to which an antiangiogenic drug, VEGFR2-antagonist DC101, radiosensitizes SDRT using murine MCA/129 fibrosarcomas and Lewis lung carcinomas, which display a dose range for SDRT lesional eradication virtually identical to that employed clinically (10–30 Gy). The gene discussed is KDR; the disease is Carcinoma, Lewis Lung.