The application of 211At in experimental tumour therapy

Astatine-211 and its short lived daughter, 211Po emit α particles which are of potential value in tumour therapy. Measurements have been made of the effect of 211At conjugated to appropriate antibodies on the development of a murine, T cell lymphoma and of human colorectal tumour xenografts in immuno-deficient mice. The likely value of 211At administered as sodium (211At) astatide, in the treatment of human thyroid carcinomas has been assessed by measuring the concentration of 211At and 125I in xenografts of such tumours in mice. Lymphoma development was prevented in 50 per cent of the mice treated with 211At-monoclonal antibody, but there was no arrest of growth or decrease in the volume of the colorectal tumour xenografts after treatment of the mice with 211At-polyclonal antibody. The differences in the response of the two types of tumour is attributed mainly to differencs in the accessibility of the malignant cells to the antibody. Xenografts of anaplastic carcinoma of the thyroid showed a ratio of concentrations tumour to blood of 3:1 for 211At and less than 1 for 125I, indicating that these tumours might be suitable for further investigations with 211At and possibly for therapy. (orig.)