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Evaluation of the biological effectiveness of L-4-boronophenylalanine in glioblastomas
Xiaohong Zhang1, Jiaomei Bai2, Diyun Shu3
1Department of Nuclear Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu Province, PR China; Key Laboratory of Advanced Nuclear Technology and Radiation Protection, Ministry of Industry and Information Technology, Nanjing, Jiangsu Province, PR China.
Purpose:
Compound biological effectiveness (CBE), arising from variances in the micro-distribution of the boron compound, is a crucial factor for converting the boron dose into the bioequivalent dose of traditional radiotherapy. This study aimed to estimate CBE values of L-4-boronophenylalanine (BPA) in glioblastomas.
Materials And Methods:
The survival fraction was utilized to evaluate the CBE value of BPA in U251 gliomas and their xenograft tumor in an accelerator-based BNCT system.
Results:
The CBE values of BPA in U251 gliomas were 4.48 at the survival fraction level of 0.37, 3.27 at 0.10, and 2.63 at 0.01. In U251 tumors, the CBE values were 7.73, 5.14, and 3.55 at the corresponding levels of the survival fraction. The CBE values in vivo/in vitro were higher than those observed in vitro. The D0 values of BNCT were 2.04 Gy for U251 gliomas and 0.63 Gy for U251 xenograft tumors. These values indicate that U251 tumor cells exhibited increased sensitivity to BNCT compared to their in vitro counterparts. Additionally, the CBE values of BPA in the U251 gliomas and their xenograft tumor significantly decreased as the survival fraction reduced, which may be attributed to insufficient cell killed at higher BNCT doses.
Conclusions:
The in vivo/in vitro experiment on U251 gliomas yielded higher CBE values of BPA than those obtained in vitro. The CBE values were strongly influenced by varying survival fraction levels. A survival fraction of 0.10 is recommended as the more suitable endpoint for assessing the CBE value in tumor control.
