Radiation effects of neutrons and protons - clinical results and potential modifications

A low OER and dose escalation capabilities are the reasons for using neutrons and protons in radiotherapy, respectively. More than 45,000 patients have been treated with both radiation qualities to date but only a limited number of clear indications have been identified. They comprise salivary gland tumours and prostate cancer for neutrons and ocular melanomas, tumours of the base of the skull and certain intracerebral lesions for protons. There is evidence that the field of indications can be enlarged when radiation effects are modified. With regard to neutrons, normal tissue protective agents could help to reduce late complications. Hyperthermia is a potential tool to increase the local tumour-control capability of neutrons and protons and has never been evaluated in these combinations. Finally, improved tumour oxygenation using hyperbaric oxygen, carbogen or a combination with nicotinamide have not yet been evaluated together with the dose escalation potential of protons. For all these potential clinical modifications, previous or accompanying radiobiological investigations are of utmost importance. (orig.)