The immunomodulating effect of interferon-gamma intravesical instillations in preventing bladder cancer recurrence.

PURPOSE The purpose is to investigate the prophylactic effect of intravesically instillated recombinant IFN-gamma against recurrence of superficial transitional cell carcinoma of the bladder and to evaluate its effect in local immune response, presumably mediating its therapeutic efficacy. EXPERIMENTAL DESIGN We prospectively randomized in two groups 123 patients with initially diagnosed superficial transitional cell carcinoma and stage Ta, T1, grade 2 tumors, who underwent transurethral tumor resection (TUR). In group A, 60 patients received IFN-gamma (1.5 x 10(7) IU/instillation), whereas 63 patients, consisting of the control group B, received mitomycin C (40 mg/instillation). The annual administration schedule consisted of eight weekly followed by four biweekly and then by eight monthly instillations for both regimens. We also analyzed the immunophenotype of the intratumoral and intramural leukocytes by immunohistochemical and flow-cytometric techniques. To this purpose, tumor samples were obtained at TUR and random biopsies at TUR and during cystoscopy at 6 and 12 months, and bladder washings were collected before TUR and at preselected time points. RESULTS In group A, 44 of 60 (73.4%) patients, and in group B, 36 of 63 (57.2%) patients, were tumor free during the median follow-up period of 26.5 months (range, 3-49 months). IFN-gamma was well tolerated. Six months after starting treatment, follicular cystitis was detected in patients responding to IFN-gamma. After IFN-gamma instillations, statistically significant increases in T cells, T-helper cells, T-cytotoxic cells, natural killer cells, and total leukocytes, as well as in the number of B cells expressing intercellular adhesion molecule-1 and total leukocytes expressing HLA-DR, were observed by flow cytometry in tissue specimens and bladder washings. CONCLUSIONS Recombinant IFN-gamma appears to be effective against stage Ta, T1, grade 2 bladder tumors' recurrence. Recruitment and activation of intramural leukocytes seem to be involved in the mechanism of IFN-gamma action.