Challenges of Ionizing Radiation in Tumor Treatment and Role of Angiogenesis.

Ionizing radiation is a non-specific, but most widely used therapeutic method for cancer treatment. However, a minor fraction of tumor cell population manages to survive after radiation. Radiation efficacy depends on adequate oxygen supply. Rapid growing tumors cause hypoxia that upregulates many pro-survival pathways. At clinical doses, radiation activates inflammatory pathways and causes oxidative stress that plays a positive role during angiogenesis. Selective targeting of signaling mechanisms may radiosensitize tumors.