IMMUNOLOCALIZATION OF TRANSITIONAL-CELL CARCINOMA OF THE BLADDER WITHINTRAVESICALLY ADMINISTERED TC-99M LABELED HMFG1 MONOCLONAL-ANTIBODY

The aim of this study was the immunolocalization of transitional cell carcinoma of the bladder with a radiolabelled murine tumour-associated monoclonal antibody and the measurement of the absolute uptake of the antibody by the tumour. Fourteen patients with transitional cell carc inoma of the bladder received 3-6 mCi (111-222 MBq) of technetium-99m labelled HMFG1 monoclonal antibody intravesically and one patient, 2 m Ci (74 MBq) of iodine-131 labelled 11.4.1, which is a non-tumour-speci fic monoclonal antibody. Four of the 15 patients were evaluated with s ingle-photon emission tomography (SPET) 1 1/2 to 2 h post administrati on. All patients underwent transurethral resection of the bladder tumo ur within 12-20 h following intravesical administration of the radiola belled antibody. The radioactivity of biopsy specimens from normal uro thelium and tumour areas were counted in a gamma counter. The mean upt ake of the radiolabelled antibodies from normal and tumour sites was e xpressed as a percentage of the administered dose per kilogram of tiss ue. Conventional histology and immunohistochemistry using HMFG1 monocl onal antibody were performed on paraffin sections of the biopsy specim ens. Although our results are preliminary, it can be concluded that: ( a) bladder tumours are well imaged by SPET when using Tc-99m-HMFG1; (b ) intravesically administered radiolabelled antibody remains on the bl adder tissue and does not escape into the systemic circulation; (c) th e wide range of tumour uptake values (0%-9.3% administered dose/kg) ob served probably ran hp attributed to heterogeneity of the antigenic ex pression of the tumour; (d) values of Tc-99m-HMFG1 monoclonal antibody uptake by the tumour do not justify future attempts at radioimmunothe rapy.