Effect of intravesical Bacillus Calmette-Guérin on detection of a urothelial differentiation antigen in exfoliated cells of carcinoma in situ of the human urinary bladder.

Flow cytometry was used to detect and quantify expression of a urothelial differentiation antigen (Om5) and nuclear DNA in exfoliated epithelial cells of the urinary bladder from 15 patients with nonpapillary carcinoma in situ during and after intravesical therapy with Bacillus Calmette-Guérin (BCG). Before BCG treatment exfoliated cells reacting with the mouse monoclonal antibody Om5 were found in 13 cases. Following treatment Om5 positive cells were still present in 9 cases but 4 patients who had had Om5 positive cells prior to BCG therapy no longer had detectable antigen-positive cells after therapy. Thus intravesical BCG therapy can alter detection of a urothelial differentiation antigen in exfoliated bladder epithelial cells. It is not certain whether this antigen or other differentiation antigens measured by flow cytometry will advance our present techniques for assessing effects of therapy on carcinoma in situ and other bladder tumors. However, five of nine patients showing persistence of Om5 positive cells after therapy were found to have recurrent tumor by biopsy and two others had positive cytology (median follow-up, 13 months). None of the four without detectable antigen-positive cells after therapy had clinical evidence of tumor by cystoscopy, biopsy, or cytology (median follow-up, 12 months). It now appears feasible and desirable to initiate clinical investigations of this and other differentiation antigens in combination with DNA by flow cytometry of bladder irrigation specimens.