A novel cancer therapy using a Mössbauer-isotope compound

Abstract

Cancer radiotherapy uses high doses of ionizing radiation (l–10²Gy; 10²–10⁴rad) because only a small fraction of the absorbed dose leads to lethal double-strand breaks in DNA. These breaks are more efficiently produced by Auger electrons (1–10 eV nm⁻¹) generated in proximity to the DNA. The energy of these electrons (on average 21 electrons for the decay of ¹²⁵I) is dissipated within 10–100 nm of the Auger event and produces multiple double-strand DNA breaks^1,2. A single Auger event can be lethal to a cell and is comparable to more than 10⁵ photon absorption events in conventional radiotherapy^3,4. We now report that ⁵⁷Fe(III).bleomycin, administered to malignant cells in vitro and in vivo and irradiated with resonant Mossbauer gamma rays (14.4 keV), causes ablation of the malignant cells, presumably by Auger cascade, with extremely small radiation doses—about 10⁻⁵ Gy. As a basis for comparison, about 5 Gy is necessary to achieve a similar effect with conventional radiotherapy⁵.