The most commonly used chemotherapeutic drugs combined with radiation as radiosensitizers are cis-platinum and 5-fluorouracil. These drugs, especially cis-platinum, are toxic to kidney, myelosuppressive and prone to cause life-threatening neutropenia, anemia or thrombocytopenia, which are more severe than those with radiotherapy alone (1-3). To avoid unnecessary over-treatment, the optimization of CCRT is of critical importance. Herein, the development of a surrogate marker for monitoring treatment efficacy as well as toxicity is pivotal to optimize CCRT.