Treatment of Transitional Cell Carcinoma of the Bladder With Intravesical Interleukin-2: A Pilot Study

Human recombinant interleukin-2 (rIL-2) administered systemically can mediate the regression of solid tumors in some patients. IL-2 has been detected in the bladder effluent from patients treated with intravesical BCG for transitional cell carcinoma of the bladder (TCC), suggesting that IL-2 may be an effector molecule in the mechanism of action of BCG. The purpose of the pilot study was to determine the response rate, duration of response and toxicity of rIL-2 (Cetus) administered intravesically to previously untreated patients and patients who had failed prior intravesical therapy with other agents. Fourteen patients with biopsy proven transitional cell carcinoma (13 Stage TIS/Ta/T1, 1 Stage T2) were treated with 8 weekly instillations ofl2X10⁶ IU of rIL-2. An index lesion was followed with cystoscopy, biopsy and cytology at three months, with identical follow up every three months thereafter if a response was noted in the index lesion at the first evaluation. There were 3 complete responses (duration of response measured from start of treatment to date of progression) of 9+, 3, 9 months; one patient with TIS, and 2 patients with Ta disease. There were 11 non-responders for an overall response rate of 21%. One patient with extensive CIS had a dramatic partial response and was converted to a complete response with a second 8-week course of rIL-2. All of the complete responders had failed prior intravesical therapy with standard agents. Toxicity from rIL-2 given intravesically was minimal. One patient reported malaise for 24 hours after each treatment and two patients developed asymptomatic lower UTIs. Chemical cystitis was not reported by any patient. Intravesical rIL-2 did not produce any organ dysfunction toxicity as measured by routine peripheral blood tests. Because rIL-2 has some activity against established TCC of the bladder and has minimal toxicity, it should be tested against BCG in patients whose TCC has been resected fully.