A new tumour marker tested in 98 patients with bladder carcinoma.

A new, indirect marker of human tumour has been tested in 98 patients with urothelial bladder carcinoma. The marker is detected by B5, a monoclonal antibody which agglutinates erythrocytes from tumour-bearing patients. Patients admitted for cystoscopy for diagnosis of bladder tumour, or for follow-up of known disease, were chosen to enable comparison between (a) B5 results and (b) visual assessment of tumour growth. Ninety per cent of those with new tumour (20) and, overall, 80% of patients with tumour (74), were B5 positive. These results were independent of tumour size and include very small recurrences, implying that B5 is a sensitive marker of tumour presence. The background incidence of B5 positive individuals is 18% in controls; a similar incidence occurs in patients who have been tumour-free for 9 months or more. Patients who had no visible tumour in this study, but who had tumour within 9 months, were often B5 positive (6/11). This may be due to the lifespan of erythrocytes causing a delay in change from B5 positive to B5 negative in those patients who will remain disease-free.