Dose calculation in Sprague-Dawley rats affected by limb osteosarcoma for BNCT in vivo tests at the TRIGA reactor in Pavia

Osteosarcoma is the most common non-hematologic primary cancer that affects bones. The patients are typically very young, being the first incident peak between 10 and 20 years old. The conventional treatment is multiagent chemotherapy combined with extensive surgical resection, which can require the amputation of the entire limb. Nevertheless, the infiltrative growth of the tumour leads to a high incidence of local and distant recurrences that reduce the percentage of cured patients to less than 60%. Because of these poor outcomes, the identification of a new treatment option is very timely. A research project on the BNCT for osteosarcoma is ongoing at the University of Pavia. To perform the experiments, a suitable animal model has been developed, using immunosuppressed Sprague-Dawley rats inoculated with 2•107 UMR-106 cells through the femoral condyle. To load the tumour cells with 10B, innovative carriers, based on liposomes and nanoparticles and developed at the Universities of Florence and of Piemonte Orientale, are used. The in vivo experiments are performed at the thermal neutron facility of the TRIGA research nuclear reactor in Pavia. The original thermal column has been modified to house an irradiation chamber characterized by a non collimated neutron field with a low contamination of epithermal and fast neutrons as well as of photons. To spare the healthy organs of the animal, the irradiation set-up has been designed and optimized using the simulation code MCNP. In particular, a suitable neutron shield made of 95% 6Li enriched carbonate is used. The talk will show the results of the treatment planning, in particular the dose estimations obtained by the Monte Carlo calculations in the tumour and in the radiosensitive organs.