The role of mitomycin C in intermediate-risk non–muscle-invasive bladder cancer: a systematic review and meta-analysis

Background and objective: Intravesical mitomycin C (MMC) instillations are recommended to prevent recurrence of intermediate-risk non-muscle-invasive bladder cancer (IR-NMIBC); however, the optimal regimen and dose are uncertain. Our aim was to assess the effectiveness of adjuvant MMC and compare different MMC regimens in preventing recurrence. Methods: We performed a comprehensive search in PubMed, Scopus, and Web of Science in November 2023 for studies investigating recurrence-free survival (RFS) among patients with IR-NMIBC who received adjuvant MMC. Prospective trials with different MMC regimens or other intravesical drugs as comparators were considered eligible. Key findings and limitations: Overall, 14 studies were eligible for systematic review and 11 for meta-analysis of RFS. Estimates of 1-yr, 2-yr, and 5-yr RFS rates were 84% (95% confidence interval [CI] 79-89%), 75% (95% CI 68-82%), and 51% (95% CI 40-63%) for patients treated with MMC induction plus maintenance, and 88% (95% CI 83-94%), 78% (95% CI 67-89%), and 66% (95% CI 57-75%) for patients treated with bacillus Calmette-Guérin (BCG) maintenance, respectively. Estimates of 2-yr RFS rates for MMC maintenance regimens were 76% (95% CI 69-84%) for 40 mg MMC (2 studies) and 66% (95% CI 60-72%) for 30 mg MMC (4 studies). Among the studies included, BCG maintenance provided comparable 2-yr RFS to 40 mg MMC with maintenance (78% vs 76%). RFS did not differ by MMC maintenance duration (>1 yr vs 1 yr vs <1 yr). Conclusions and clinical implications: MMC induction and maintenance regimens seem to provide short-term RFS rates equivalent to those for BCG maintenance in IR-NMIBC. For adjuvant induction and maintenance, 40 mg of MMC appears to be more effective in preventing recurrence than 30 mg. We did not observe an RFS benefit for longer maintenance regimens. Patient summary: For patients with intermediate-risk non-muscle-invasive bladder cancer, bladder treatments with a solution of a drug called mitomycin C (MMC) seem to be as effective as BCG (bacillus Calmette-Guérin) in preventing recurrence after tumor removal. Further trials are needed for stronger evidence on the best MMC dose and treatment time.