Evaluation of the dose enhancement of combined ¹⁰B + ¹⁵⁷Gd Neutron Capture Therapy (NCT)

An innovative molecule, GdBLDL, for boron neutron capture therapy (BNCT) has been developed and its effectiveness as a BNCT carrier is currently under evaluation using in vivo experiments on small animal tumour models. The molecule contains both ¹⁰B (the most commonly used NCT agent) and ¹⁵⁷Gd nuclei. ¹⁵⁷Gd is the second most studied element to perform NCT, mainly thanks to its high cross section for the capture of low-energy neutrons. The main drawback of ¹⁵⁷Gd neutron capture reaction is the very short range and low-energy secondary charged particles (Auger electrons), which requires ¹⁵⁷Gd to be very close to the cellular DNA to have an appreciable biological effect. Treatment doses were calculated by Monte Carlo simulations to ensure the optimised tumour irradiation and the sparing of the healthy organs of the irradiated animals. The enhancement of the absorbed dose due to the simultaneous presence of ¹⁰B and ¹⁵⁷Gd in the experimental set-up was calculated and the advantage introduced by the presence of ¹⁵⁷Gd was discussed. (authors)