Figure 5.

A schematic drawing illustrating the two models of radiation carcinogenesis. The somatic mutation hypothesis assumes that radiation exposure may add one mutation in epithelial stem cells and thereby increasing the risk of developing cancer. In contrast, the EOH model assumes that DNA damage to the microenvironment in normal tissues may lead to an altered microenvironment which acts to produce conditions favorable for tumor cell growth through the secretion of various signaling factors (solid arrows).