Boron-10 Distribution of p-Boronophenylalanine in the Experimental Brain Tumor in the Rats

Abstract

Boron neutron capture therapy (BNCT) has been employed in the treatment of malignant brain tumor in human. In this type of radiation therapy, biodistribution of 10B in tumor and peritumoral tissue is highly important because a range of α-particle produced by n-α reaction is quite short in biological tissue. Many boron compounds have been tested to achieve an optimal biodistribution for BNCT, and sodium borocaptate (BSH) has been believed to be the one giving such distribution.1,2 BSH-based BNCT, therefore, has been employed in the treatment of glioblastoma. Another boron compound recently used in BNCT for brain tumor is para-boronophenylalanine (BPA). Although BPA is a standard boron compound for BNCT against melanoma, it is well known to accumulate in brain tumor tissue more extensively than BSH, indicating its therapeutic potential for glioblastoma.3 Unlike BSH, however, BPA is considered to easily penetrate into normal brain tissue. A safety of BPA-based BNCT has not been proven and pre-clinical study to confirm its detailed biodistribution using experimental animals must be essential. The objective of this study is to measure the boron concentrations achieved by BPA in various organs in tumor-bearing rats, including brain tumor and other major structures around the head, and compare to those achieved by BSH.