Transitional Epithelium of Urinary Bladder: Dosimetric Data for Cells at Risk in Nuclear Medicine

Most human tumors arise in epithelial tissues that serve in a secretory and protective manner. This role has been recognized in cancers of the respiratory and alimentary tracts, and the skin with cells at radiogenic risk identified and addressed in the dosimetry. Nine out of ten urinary bladder cancers arise within the transitional epithelium of the bladder. The transitional epithelium is a stratified epithelium in which the shape of the surface cells depends on the degree of stretching as the bladder fills. The epithelium is supported by basal cells that lie above a basement membrane separating the epithelium from the stroma of the bladder wall. The depth of the basal cell depends on the urine content of the bladder. Data derived in this paper suggest that the absorbed dose to the basal cells at risk is poorly represented by the absorbed dose to the bladder wall. Furthermore, the cells at risk may not even be irradiated by alpha emissions within the bladder urine content. These overestimates of the bladder dose can impact acceptance of new therapeutic radiopharmaceuticals.