Chapter 27: Radiopharmaceutical Therapy (RPT)

Radiopharmaceutical therapy (RPT) involves the systemic application of radioactive isotopes to target cancer. RPT is sometimes referred to by the more general term radioligand therapy (RLT). Most commonly, the radioactive isotope (often a beta-minus emitter) is conjugated to some form of ligand. The ligand might be an antibody that binds to a protein on the cell surface, a peptide or small molecule that binds to receptors on the tumor cell, or it may be a nanoparticle. Whatever the mechanism, the radioligand is localized to the tumor cell, and when decay occurs, the cell is killed. Because of this biological targeting, RPT agents have a differential killing effect on tumor cells compared to normal cells, where they are not localized as efficiently. This mechanism of action is relatively simple, relying only on the presence of a protein on the tumor cell or some other form of localization. The cytotoxic activity relies solely on the decaying isotope and its impact on cellular DNA, unlike other targeted molecular therapies that depend on the detailed underlying actions of molecular signaling or other processes in the cell.