First experimental proof of Proton Boron Capture Therapy (PBCT) to enhance protontherapy effectiveness

Protontherapy is hadrontherapy's fastest-growing modality and a pillar in the battle against cancer. Hadrontherapy's superiority lies in its inverted depth-dose profile, hence tumour-confined irradiation. Protons, however, lack distinct radiobiological advantages over photons or electrons. Higher LET ( Linear Energy Transfer) C-12-ions can overcome cancer radioresistance: DNA lesion complexity increases with LET, resulting in efficient cell killing, i.e. higher Relative Biological Effectiveness (RBE). However, economic and radiobiological issues hamper C-12-ion clinical amenability. Thus, enhancing proton RBE is desirable. To this end, we exploited the p + B-11 -> 3 alpha reaction to generate high-LET alpha particles with a clinical proton beam. To maximize the reaction rate, we used sodium borocaptate (BSH) with natural boron content. Boron-Neutron Capture Therapy (BNCT) uses B-10-enriched BSH for neutron irradiationtriggered alpha particles. We recorded significantly increased cellular lethality and chromosome aberration complexity. A strategy combining protontherapy's ballistic precision with the higher RBE promised by BNCT and C-12-ion therapy is thus demonstrated.