Metal-enhanced radiotherapy: Gold nanoparticles and beyond

In order to improve locoregional tumor control obtainable with radiation therapy (RT) alone, many approaches have been used. In the past decade, focus of interests was on metal-enhanced RT as metal nanoparticles (NP) held promise in simulation studies as well as both in vitro and in vivo radiosensitizing investigations. Gold NPs have predominantly been studied showing unequivocally great potential for radiosensitization. In clinical scenarios, however, it is presently limited due to less sensitization when megavoltage beams (mostly used in clinic) are compared to kilovoltage beams. A number of other metal NPs are also under investigation as well as combination of RT-NP with either classical chemotherapy or targeted agents and other cancer treatments (hyperthermia, photodynamic therapy). Ultimately, more clinical studies are needed to verify these promising results in clinical setting.