APPROACH: For a thorough understanding of the molecular processes underlying tissue responses to radiation damage, the investigators propose a genomic analysis. Their working hypothesis is that rectal and bladder toxicity will be correlated to patient genetics as measured by single nucleotide polymorphisms (SNPs) in a select group of genes. The criteria for selecting SNPs will be based on evidence for the various genes implicated or demonstrated in DNA repair pathways and radiation-induced tissue damage. In addition, since radiation injury can be considered a phenotypic tissue response to RT in genetically predisposed individuals, the investigators will examine the protein profile "signature" in sera from patients who have suffered significant toxicity. Analysis of these data will be unique in that the investigators will use both statistically based bioinformatics approaches, and biophysical modeling. This proposal represents the most comprehensive exploration to date of the concept of a molecular "signature" of normal tissue radiation injury of which the applicants are aware.