Neutron capture therapy research in Australia.

Neutron capture therapy research in Australia has continued to grow since the first Australia-Japan workshop in April, 1986. The support base has broadened and the wide range of contributing laboratories includes universities, research institutes, and hospitals. Considerable progress has been made in boron chemistry--an accurate boron assay technique has been developed, boron analogues of chlorpromazine and thiouracil have been synthesised or nearly so, and decaborane conjugation with monoclonal antibodies has been achieved to the required loadings. In vitro cell survival experiments are proceeding in the Moata reactor using human melanoma and mouse cell lines incubated with enriched boronophenylalanine and boron tetraphenyl porphyrins. Electron microscopy examination of radiation damaged morphology shows considerable differences between cell lines. Progress with the nude mouse human melanoma model has been slow because of the lack of a reliable in vivo melanotic melanoma line, and the B16 mouse line is found to be more efficacious. Tailored beam calculations for the 10 MW HIFAR reactor indicate the difficulty of obtaining a suitable therapeutic beam because of the generated gamma dose in the beam filters. A new approach to NCT utilises the enormous cross section of 157Gd and the induced-Auger effect which has been shown to cause double strand breaks in circular DNA.