Feasibility study on the utilization of boron neutron capture therapy (BNCT) in a rat model of diffuse lung metastases.

In order for boron neutron capture therapy (BNCT) to be eligible for application in lung tumour disease, three fundamental criteria must be fulfilled: there must be selective uptake of boron in the tumour cells with respect to surrounding healthy tissue, biological effectiveness of the radiation therapy and minimal damage or collateral effects of the irradiation on the surrounding tissues. In this study, we evaluated the biological effectiveness of BNCT by in vitro irradiation of rat colon-carcinoma cells previously incubated in boron-enriched medium. One part of these cells was re-cultured in vitro while the other was inoculated via the inferior vena cava to induce pulmonary metastases in a rat model. We observed a post-irradiation in vitro cell viability of 0.05% after 8 days of cell culture. At 4 months follow-up, all animal subjects in the treatment group that received irradiated boron-containing cells were alive. No animal survived beyond 1 month in the control group that received non-treated cells (p<0.001 Kaplan-Meier). These preliminary findings strongly suggest that BNCT has a significant lethal effect on tumour cells and post irradiation surviving cells lose their malignant capabilities in vivo. This radio-therapeutic potential warrants the investigation of in vivo BNCT for lung tumour metastases.