[Journal] Treatment planning of boron neutron capture therapy for hard-to-treat recurrent breast cancer

 This retrospective study aimed to investigate the feasibility of treating hard-to-treat recurrent breast cancer using boron neutron capture therapy (BNCT). In-house treatment planning system THORplan was used for the treatment planning dose calculation. Dose limits of critical organs in photon therapy were converted to BNCT dose limits. The result showed that by using two-field irradiation to cover the large tumor area, it was possible to deliver 18.5 Gy-w to 80 % of GTV and 20 Gy-w if bolus was used. The use of bolus which shifted the thermal neutron flux peak towards skin surface, reduced dose delivered to internal organs, such as heart, liver and lung. Even with longer irradiation time, the mean dose of heart could be reduced by >15 % and the mean dose of liver could be reduced by > 24 %. This study showed that it is feasible to use BNCT for this hard-to-treat recurrent breast cancer.