The tumor stroma plays an important role in the response to high-dose per fraction radiation treatment because the vascular endothelial cell apoptosis is rapidly activated above 10 Gy per fraction (Garcia-Barros et al., 2003), and that the ceramide pathway orchestrated by acid sphingomyelinase (ASMase) operates as a rheostat that regulates the balance between endothelial survival and death and thus tumor response (Truman et al., 2010). This evidence concerns the gene SMPD1 and neoplasm.