RBEs of Thermal Neutron Capture Therapy and ¹⁰B(n,α)⁷ Li Reaction on Melanoma‐Bearing Hamsters

Abstract

Using Greene's melanoma transplanted into Syrian (golden) hamsters, we determined the relative biological effectiveness (RBE) of thermal neutron capture therapy (TNCT) using 10B-paraboronophenylalanine (10B-BPA) in comparison with a 9-MeV electron beam. We also obtained the RBE of the 10B(n, alpha)7 Li reaction by calculation based on summed dose data from TNCT. Throughout this study, the Kyoto University Research Reactor was used as the source for thermal neutrons; the reactor was specially altered to attain a low contamination level both for gamma-rays and fast neutrons. 10B-BPA was administered 8 hours before thermal neutron irradiation to the hamsters with melanoma. The tumor was then irradiated at 5 MW for 90 minutes. The absorbed dose from this TNCT was calculated by the method of Fairchild and Goodman (Phys. Med. Biol. 1966; 2:15-30). The RBEs of the TNCT and the 10B(n, alpha)7 Li reaction obtained by the tumor growth delay time (TGDT) method were 2.22 and 2.51, respectively, at 10.5 days of TGDT. These RBE values varied with TGDT and the absorbed dose. The RBE value of TNCT had a peak at 7.0 days of TGDT; that of the 10B(n, alpha)7Li reaction was higher at a low absorbed dose level and lower at a high absorbed dose level.

Boron Neutron Capture Therapy (BNCT) for Cutaneous Malignant Melanoma Using 10B-p-Boronophenylalanine (BPA) with Special Reference to the Radiobiological Basis and Clinical Results

“…Although there were only three in vivo studies on this issue ( Table 1 ), the RBE values of BNCT mixed beam for melanoma control were relatively consistent ranging from 2.0 to 2.22. The only in vivo data for the CBE value of the 10 B (n, α) 7 Li reaction for melanoma control was 2.5, as reported by Hiratsuka [ 28 ].…”

“…Hiratsuka et al [ 28 ] investigated the RBE of the 10 B(n, α) 7 Li reaction for the control of hamster melanoma. Hamsters bearing Green’s melanoma were intravenously administered with 10, 20, and 40 mg of BPA 8 h before thermal neutron irradiation.…”

Biodistribution of Boron Concentration on Melanoma‐bearing Hamsters after Administration of p‐, m‐, o‐Boronophenylalanine

“…This melanoma was allowed to proliferate subcutaneously in male Syrian (golden) hamsters 16) until it reached 10 mm in diameter, 14 days after implantation, at which time the experiments were performed. p-, m-, o-BPA were synthesized from natural-abundance boron (Fig.…”

New Era of Cell Re‐Discovery Led to the Control of Melanogenesis/Melanoma: A Scientific Journey into Terra Incognita

“…Radiobiological and radiotherapeutic analyses leading to pre-clinical studies to pro6e and refine efficacy and safety: In vitro radiobiological studies using cultured melanoma cell lines (46) and radiotherapeutic studies using Greene's melanoma-bearing hamsters have been extensively carried out. The relative biological effectiveness of our BNCT was 2.22 based on the comparative evaluation of re-growth curves of hamster melanoma following treatment by g-ray (cobalt) and BNCT (47). Based on these findings, we began pre-clinical studies.…”