Bromine-80m radiotoxicity and the potential for estrogen receptor-directed therapy with auger electrons.

While theoretically feasible, estrogen receptor (ER)-directed radiotherapy of hormone-dependent cancers has not been realized because no ER-seeking ligand with an appropriate radiotoxic potential has been identified. Since an appropriate nuclide is a key component we studied the 4.4-h half-life, Auger electron-emitting nuclide bromine-80m. When incorporated into DNA this nuclide was radiotoxic to cells in culture and caused substantial chromosomal damage, while similar concentrations of bromine-80m as bromide or bromoantipyrine were without effect. The mean lethal dose for bromine-80m was 45 atoms per nucleus which is consistent with use in receptor-positive cancers with limited numbers of ER.