Boron neutron capture therapy (BNCT) for experimental bladder cancer: systemic or intravesical approach

BACKGROUND: To investigate the antitumoral and pro-inflammatory effect of Boron Neutron Capture Therapy (BNCT) following systemic or intravesical borophenilalanine administration, and to compare it with conventional radiotherapy (cRT) in an experimental bladder cancer (BC) model. METHODS: Sixty-four Wistar rats were used, of which half were exposed to carcinogen to induce BC. Radiation therapy (RT) was performed both in the MARK TRIGA-II reactor for BNCT and in the Radiation Oncology divison for cRT. After necropsy, bladder and perivesical tissues were collected. Tumour staging, tumour burden, proliferative, and apoptotic indexes were evaluated for bladder samples. Bladder and perivesical tissues (colon, uterus, and anterior abdominal wall) were also assessed for inflammatory changes in H&E-stained sections, and also bladder TNF-α expressions was examined by immunohistochemistry and Western blot. RESULTS: The animals with cancer had a 15-30% decrease in tumour burden after RT. The incidence of persistent papillary urothelial carcinoma was 100% in the Cancer-cRT group and 87.5% in the Cancer-BNCT-Sys group, whereas a lower incidence was observed in the Cancer-BNCT-IV group (71.4%). A lower proliferative and a higher apoptotic indexes were observed in Cancer-BNCT-IV group compared to Cancer-cRT. Immunohistochemistry and Western blot for TNF-α expression showed that pro-inflammatory response in bladder was lower in BNCT-IV group among cancer treated groups. Moreover, there were lower proinflammatory adverse findings in perivesical tissues, including colon and uterus, in animals receiving BNCT-IV. CONCLUSION: Similar to cRT, systemic or intravesical BNCT resulted in a partial decrease in tumour burden, but fewer adverse findings by intravesical borophenilalanine.