Background: Adjuvant intravesical Bacillus Calmette-Guerin (BCG) treatment after resection of non invasive superficial bladder cancer has been shown to significantly decrease tumor recurrence. However, the serious local and systemic side-effects of this treatment have promoted the use of other immunoactive substances, which, to date, have all failed to show efficacy equal to BCG therapy.
Patients and methods: In the present phase I/II clinical trial, an aqueous mistletoe extract, standardized to mistletoe lectin, was applied intravesically to 30 patients with superficial urothelial bladder carcinomas of stages pTa and pT1, grades 1 to 2. After transurethral resection, each patient received 6 instillations at weekly intervals of 50 ml of the extract with mistletoe lectin concentrations between 10 ng/ml and 5000 ng/ml. This was retained in the bladder for 2 hours. Three patients per group received a dose, which was then doubled in the next group. The clinical follow-up consisted of examinations by cystoscopy, cytology and random biopsies.
Results: Within the observation time of 12 months, 9 patients had tumor recurrence, while 21 patients remained tumor-free. This recurrence rate was comparable to that of local historical controls with superficial bladder cancer of the same stages and grades that had been treated with adjuvant BCG. The tolerability of the intravesically-administered mistletoe extract was very good. None of the study patients had local or systemic side-effects according to the WHO classification 1-4.
Conclusion: From these results, it is concluded that the standardized mistletoe extract could be a potential adjuvant therapy for superficial bladder cancer. Further studies may show the optimal intravesical treatment regimen.