Radiation-induced cognitive impairment

Radiation-induced cognitive impairment is one of the late adverse effects of cranial radiation therapy (CRT) for cancer patients with primary and metastatic brain tumors, head and neck cancers etc. It affects approximately 40-50% patients who survive for >6 months and severely reduces the quality of survivors' life. With the advancement of radiation therapy technology, the survival of brain tumor patients is significantly improved, thus understanding the etiology of CRT-induced cognitive impairment and developing the potential strategies of the management of this side-effect have become more important than ever. Some valuable insights have been obtained through extensive preclinical studies. It is suggested that radiation-induced cognitive impairment is due to the dysfunctions of hippocampus-dependent learning, memory and spatial information processing after radiation exposure. Until now, research results have shown that radiation-induced cognitive impairment and neurodegenerative disorders such as Alzheimer disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and aging-related cognitive decline, share some similar pathogenic factors, including chronic oxidative stress and inflammation, impairment in neurogenesis and angiogenesis. Blockade of these factors by antioxidants, anti-inflammatory drugs, transplant of neural stem cells, systemic hypoxia etc. can significantly ameliorate cognitive decline in cranially irradiated experimental animals. These studies shed the light on the pathogenesis of radiation-induced cognitive impairment and may have important implication in developing novel therapeutic interventions for surviving cancer patients who suffer from cognitive decline after CRT.