Background: Adjuvant instillation therapy with chemo- or immunotherapeutic agents is an integral component in the treatment of non-muscle-invasive bladder cancer. There is, however, no general consensus on the choice of medication and the optimal duration of therapy. This multicenter trial compared a long-term treatment regimen with mitomycin C (MMC) with two short-term treatment approaches with MMC or bacille Calmette-Guérin (BCG) for intermediate-/high-risk bladder tumor after transurethral resection. In patients with low-risk bladder tumors, the effectiveness of six weekly MMC instillations was determined and compared with the results of patients not receiving adjuvant treatment.
Material and methods: A total of 495 patients with intermediate-/high-risk bladder tumor (recurrent and/or multifocal pTaG1, pTaG2-3, or pT1G1-3) were randomly administered either BCG-RIVM 2x108 CFU in six weekly instillations, MMC 20 mg in six weekly instillations, or MMC 20 mg in six weekly instillations with subsequent monthly instillations for 3 years. A total of 132 low-risk patients (first diagnosis of a unifocal pTaG1 bladder tumor) were randomly allocated to two treatment arms. In the first arm, 20 mg MMC were instilled weekly six times. In the control arm, the patients received no adjuvant therapy.
Results: The 3-year recurrence-free rate in the patients of the intermediate-/high-risk group was 65.5% (95% CI: 55.9-73.5%) in the BCG arm and 68.6% (95% CI: 59.9-75.7%) in the MMC short-term arm. In the MMC long-term arm, the 3-year recurrence-free rate was significantly higher at 86.1% (95% CI: 77.9-91.4%, log-rank test: p=0.001). There was no increased toxicity observed with long-term administration of MMC. In the low-risk group, the 3-year recurrence-free rate after adjuvant therapy was 74% (95% CI: 60.0-83.8%) and in the patients receiving no adjuvant treatment 63% (95% CI: 46.6-75.5%, corresponding to a hazard ratio of 0.58 (95% CI: 0.28-1.18%). The difference between the treatment arms was not significant.
Conclusion: Long-term prophylaxis with MMC results in a significantly reduced recurrence rate in intermediate-/high-risk bladder cancer with a comparable toxicity profile in comparison to short-term MMC or short-term BCG. Our study showed no significant decrease of the recurrence rate in low-risk tumors with six adjuvant MMC instillations. This treatment approach thus does not represent an alternative to early instillation.