Abscopal Effect of Radiation Therapy: Current Concepts and Future Applications

Radiation therapy is one of the most important treatment tools in cancer therapy. It has a wide variety of indications for many malignant tumors, mostly for local control, whether a curative or palliative outcome is the intent, or as preor post-operative treatment as either neoadjuvant or adjuvant therapy. Radiation therapy is commonly used along with hormone therapy or chemotherapy. The full scope of the capabilities of radiation therapy is achieved particularly in combination settings with various anti-tumor modalities, the so-called multidisciplinary approach. To enhance the therapeutic efficacy of radiation sufficiently, one may choose radiation therapy in combination with cytotoxic chemotherapeutic agents or with warming devices used for hyperthermia treatment or utilize newly developing physical approaches as typified by intensity modulated radiation therapy, stereotactic radiation therapy, brachytherapy and image-guided radiation therapy. Moreover, an immunoenhancing agent might be selected in combination with radiation therapy from the standpoint of immunobiology in the treatment of cancer. Some promising data have been shown on the basis of immunological activation with ionizing radiation, demonstrating cytotoxic T lymphocyte (CTL) amplification and dendritic cell (DC) stimulation or maturation (Demaria, et al., 2004,Ganss, et al., 2002,Nikitina and Gabrilovich, 2001,Schuler, et al., 2003).