Laboratory research has suggested that targeting specific signalling proteins would be well suited for selectively enhancing the tumor radiosensitivity. In human xenograft models (non-small cell lung cancer and breast cancer) treated with gefitinib and irradiation, combined therapy has shown a significant increase in tumor growth delay as compared with monotherapy of irradiation or gefitinib. The epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 selectively potentiates radiation response of human tumors in nude mice, with a marked improvement in therapeutic index. The authors concluded that gefitinib profoundly enhanced the antitumor action of RT against the tested tumors without significant adverse effects, increasing the therapeutic selectively of ionizing radiation in certain model systems. Substantial benefits for this multimodality therapy in patients could be expected.