[Molecular basis and clinical results of radiation therapy combined with molecular targeted therapy]

Molecular target-based drugs combined with radiation therapy have been expected as promising approach in cancer treatment, and clinical trials using combined modalities have been performed to evaluate the feasibility and efficacy of this approach. In order to obtain maximum radiotherapeutic gain, a detailed understanding of the mechanism underlying the interaction between radiation and molecular target-based drugs is indispensable. Among molecular target-based drugs, inhibitors targeting EGFR and its signal transduction pathways have been vigorously investigated, and mechanisms regarding the radiosensitizing effect have been getting clear. In addition, the results of randomized clinical trials demonstrated that radiation therapy combined with cetuximab resulted in improvement of overall and disease-specific survival rate compared with radiation therapy in locally advanced head and neck cancer. In this review, established and potential molecular targets for potentiation of radiation-induced cell killing are summarized, especially focusing on EGFR and its signal transduction pathways; also, clinical trials of combined radiation therapy plus molecular target-based drug therapy are summarized.