A preliminary experimental study of boron neutron capture therapy for malignant tumors spreading in thoracic cavity

Background: The purpose of the present study is to verify the treatment effects of boron neutron capture therapy (BNCT) in ectopic tumors implanted in the thoracic cavity mimicking malignant pleural mesothelioma (MPM). Methods: The tumor model was created by implanting murine squamous cell carcinoma cells into the thoracic cavity. Mice were sorted into four groups: group I for non-treatment; group II for neutron irradiation; group III for gamma-ray irradiation; and group IV for BNCT irradiation. The antitumor effect was evaluated on the basis of the change in survival time. To assess the effects of BNCT on normal lung, non-tumor bearing mice were treated using the same method as done to the tumor-burdened mice. Results: The BNCT group had a longer survival time of 31 days (range 5-60), which was significantly longer than that of the non-treated control group (P = 0.011), but not significantly different from that of the neutron and gamma-ray groups (P = 0.067 and 0.094, respectively). In the BNCT and neutron groups, incidence of minimal lung fibrosis was significantly higher compared with the non-treated control group (P = 0.003 and 0.04, respectively). Conclusions: BNCT is a potentially promising treatment for malignant tumors spreading in the thoracic cavity such as MPM.