Quantitation of antibody uptake in spontaneous metastases.

A procedure of high resolution quantitative autoradiography was established and tested in the murine ESb-Mp lymphoma system. Using 125I-labelled antibody 12-15A, liver metastases with diameters down to 100 microns were identified and intralesional radioiodine accumulation was assessed as % injected dose (iD) g-1. Uptake was found to be highest in intermediate size metastases, i.e., up to 100% iD g-1 in 1 mm lesions, while it gradually declined with both increasing and decreasing diameters of metastases. Lower uptake in large size metastases was due to a marked non-uniformity in radioactivity retention, while lower uptake in small metastases was possibly due to insufficient access of the antibody to intrahepatic processes which have not yet established an autonomous blood supply.