Major compound-dependent variations of sup 10 B(n. alpha. ) sup 7 Li RBE for the 9L RAT gliosarcoma in vitro and in vivo

Abstract

Relative biological effectiveness (RBE) values for the high linear-energy-transfer (LET) radiations produced during born neutron capture therapy (BNCT) were determined using the 9L rat gliosarcorna both in vitro and as an intracerebral tumor. In the absence of {sup 10}B, the combined effect of the recoiling protons from the {sup 14}N(n,p){sup 14}C and the {sup 1}H(n,n{prime})p reactions, compared to an iso-effect endpoint produced by 250 kVp x-rays, yielded RBEs for these high-LET protons of 4.4 in vitro and 3.8 in an in vivo/in vitro assay. RBEs for the {sup 10}B(n,{alpha}){sup 7}Li reaction were calculated from cell survival data following reactor irradiation in the presence or in the absence of the either of the amino acid, p-boronophenylalanine (BPA) or the sulfhydryl dodecaborane dimer (BSSB). With BPA, RBE values ranged from 3.5 to 11.4, while under the same set of conditions with BSSB, RBE values ranged from 1.1 to 4.3. In vitro, higher RBEs for the {sup 10}B(n,{alpha}){sup 7}Li reaction using BPA than with BSSB suggest a difference in distribution of {sup 10}B relative to the nucleus