[Radiotherapy of high grade glioma: use of fast neutrons, therapy and enhancement by neutron capture].

Among high linear energy transfer (LET) irradiations techniques, those using fast neutrons are able to eradicate glioblastoma cells. At least a 13 grays (Gy) irradiation dose has to be used, but high morbidity is observed in case of over 11 Gy irradiation. So, no therapeutic windows have been found despite the fact that more than 900 patients were included in clinical trials. Boron neutron capture therapy (BNCT) uses alpha emitting nuclear reactions, produced within tumoral cells by boron neutron captures. (10)B is specifically loaded inside tumoral cells via a boronated molecule, and the tissues are then irradiated with thermal or epithermal neutrons. Although this type of irradiation is yet considered as a regular method in Japan, USA and Europe have started clinical trials, currently in progress, in order to define the BNCT place in the post-operative care of high grade glioma. Non-removable tumors may benefit from boron neutron capture enhancement of fast neutron irradiation, i.e. the combination of these two methods. Preliminary studies show that a "biological" dose enhancement of 20 % could be obtained within the tumor when a concentration of 100 microg/g of (10)B is targeted into it. These concentrations are achievable by intra-arterial administration of (10)boronophenylalanine (BPA) or borosulfhydryl (BSH). Recently, some publications have also demonstrated that the thermal neutron flux yielded within the irradiated tissues could be increased. Clinical trials, using this technique, are planned in USA and Europe.