In vivo studies on the uptake of radiolabelled antibodies by colorectal and gastric carcinoma xenografts.

A number of criteria have been investigated to try to improve the uptake of radiolabelled antibodies by colorectal carcinoma xenografts. The in vivo behaviour of four antibodies was compared and found to vary. Two antibodies, 11-285-14 and 14-95-55, demonstrated specific uptake by the tumours. 11-357-5 was lost from the tumour after 72 h and the fourth antibody could not be iodinated without loss of activity. Neither increased time nor increased dose were shown to increase the uptake of antibody by tumours although the clearance of antibody from blood was shown to be more rapid than from tumour resulting in clearer backgrounds. Increased tumour:blood ratios were demonstrated by particular combinations of antibodies but the extent to which this occurred varied with the epitopes recognised. High carcinoembryonic antigen expressing xenografts did not show significantly higher uptake of antibody. This was shown to be due to the smaller size of these tumours and associated decreased vascularity.