Purpose: Adjuvant intravesical immunotherapy with bacillus Calmette-Guerin (BCG) for noninvasive superficial bladder cancer has been shown to decrease tumor recurrence significantly. However, serious local and systemic side effects of this treatment have promoted the use of other immunoactive substances, which to date have failed to show efficacy equal to that of BCG immunotherapy.
Materials and methods: In the current phase I/II clinical trial an aqueous mistletoe extract standardized to mistletoe lectin was administered intravesically to 30 patients with superficial urothelial bladder carcinoma. About 4 weeks after transurethral resection each patient received 6 instillations at weekly intervals of 50 ml extract with mistletoe lectin concentrations between 10 and 5,000 ng/ml, which was retained in the bladder for 2 hours. Three patients per group received a dose, which was then doubled in the next group. Clinical followup consisted of examinations with cystoscopy, cytology and random biopsies. To detect cytokines and tumor necrosis factor-p75 receptor venous blood and urine samples were taken before instillation, and 2, 6 and 24 hours thereafter.
Results: The tolerability of intravesically administered mistletoe extract was good at all applied concentrations. None of the patients had local or systemic side effects according to WHO classification 1-4. Within the 12-month observation time study patients with pTa G2 and pT1 G2 tumors showed a recurrence rate of 33%, comparable to that in a local historical control group of patients with equal stage and grade who were treated with adjuvant BCG. Comparison of urine cytokine levels before instillation, and 2, 6 and 24 hours thereafter brought about no significant alterations in all measured cytokines.
Conclusions: From these results it is concluded that standardized mistletoe extract could be a potential alternative adjuvant therapy for superficial bladder cancer. Nevertheless, the optimal intravesical treatment regimen has yet to be defined.