Boron neutron capture therapy (BNCT) combines selective accumulation of (10)B carriers in
tumor tissue with subsequent neutron irradiation. We previously demonstrated the therapeutic efficacy of BNCT in the hamster cheek pouch
oral cancer model. Optimization of BNCT depends largely on improving
boron targeting to
tumor cells. Seeking to maximize the potential of BNCT for the treatment for
head and neck cancer, the aim of the present study was to perform
boron biodistribution studies in the
oral cancer model employing two different
liposome formulations that were previously tested for a different pathology, i.e., in experimental mammary
carcinoma in BALB/c mice: (1) MAC:
liposomes incorporating K[nido-7-CH(3)(CH(2))(15)-7,8-C(2)B(9)H(11)] in the bilayer membrane and encapsulating a hypertonic
buffer, administered intravenously at 6 mg B per kg
body weight, and (2) MAC-TAC:
liposomes incorporating K[nido-7-CH(3)(CH(2))(15)-7,8-C(2)B(9)H(11)] in the bilayer membrane and encapsulating a concentrated aqueous
solution of the hydrophilic species Na(3) [ae-B(20)H(17)NH(3)], administered intravenously at 18 mg B per kg
body weight. Samples of
tumor, precancerous and normal pouch tissue, spleen, liver, kidney, and blood were taken at different times post-administration and processed to measure
boron content by inductively coupled plasma mass spectrometry. No ostensible clinical toxic effects were observed with the selected formulations. Both MAC and MAC-TAC delivered
boron selectively to
tumor tissue. Absolute
tumor values for MAC-TAC peaked to 66.6 ± 16.1 ppm at 48 h and to 43.9 ± 17.6 ppm at 54 h with very favorable ratios of
tumor boron relative to precancerous and normal tissue, making these protocols particularly worthy of radiobiological assessment.
Boron concentration values obtained would result in therapeutic BNCT doses in
tumor without exceeding radiotolerance in precancerous/normal tissue at the thermal neutron facility at RA-3.