Mitomycin C vs. Bacillus Calmette–Guerin for treatment of intermediate-risk nonmuscle invasive bladder cancer patients—A comparative analysis from a single center

Background Induction followed by 1 year maintenance instillation of intravesical Bacillus Calmette–Guerin (BCG) is the standard treatment for intermediate-risk (IR) nonmuscle invasive bladder cancer (NMIBC) patients. Few data exist on the efficacy of Mitomycin C (MMC) instillation in this setting. Methods We retrospectively analyzed 226 IR-NMIBC patients classified by the International Bladder Cancer Group (IBCG) and 250 IR-NMIBC intravescical treatment-naïve patients classified by the European Association of Urology (EAU). All patients received either a full induction course of BCG or 40 mg/40 ml MMC from 2012 to 2022. Optimal treatment was defined as 1-year maintenance for BCG and 11 monthly maintenance instillations for MMC. Kaplan–Meier analysis estimated recurrence-free survival (RFS) before and after inverse probability of treatment-weighting (IPTW) and progression-free survival (PFS). Multivariable Cox regression was used to evaluate difference in recurrence after adjustment for clinically relevant variables before and after IPTW. Results Optimal BCG and MMC courses were administered to 21% of IR-IBCG and 23% of IR-EAU patients. At 4-years, patients treated with optimal MMC and BCG treatment had similar RFS and PFS in both EAU and IBCG groups. Patients receiving nonoptimal BCG compared to optimal MMC exhibited lower 4-year RFS after IPTW (82% vs. 68% in EAU and 82% vs. 65% in IBCG). At 4-year optimal MMC had greater PFS non optimal BCG. Optimal MMC treatment predicted recurrence in EAU (adjusted and weighted HR 0.33, 95% CI, 0.11-0.98) and IBCG (adjusted and weighted HR 0.29, 95% CI, 0.08-0.97) groups compared to nonoptimal BCG. Conclusions Optimal 40 mg/40 ml MMC treatment was as effective as optimal BCG in IR-IBCG and IR-EAU NMIBC patients, reducing both recurrence and progression compared to nonoptimal BCG. MMC could be a valid first line alternative to BCG for both IR-EAU and IR-IBCG intravescical treatment-naïve patients, during BCG shortages.