Institutional adherence, complication rates, and intravesical recurrence with intraoperative mitomycin C during...

We evaluated institutional adherence, complication rates, and intravesical recurrence (iVR) with intraoperative intravesical mitomycin C (MMC) instillation immediately after bladder cuff closure during radical nephroureterectomy (RNU) for upper urinary tract urothelial carcinoma (UTUC).

This retrospective single-centre study included patients with UTUC who underwent RNU at Zealand University Hospital (2017-2023). The primary endpoint was adherence to the intraoperative intravesical MMC protocol following its implementation in 2018. Secondary endpoints were 90-day postoperative complications (Clavien-Dindo classification [CDC]) and iVR within 24 months. Cumulative incidence functions accounted for death as a competing event, and multivariable Fine-Gray regression was performed.

Among 140 patients who underwent RNU, 101 received intraoperative intravesical MMC while one received it postoperatively. The institutional adherence cohort comprised 116 patients treated after protocol implementation, of whom 99 (85.3%) received MMC. Among the 17 who did not, reasons were bladder leakage (8, 47.1%), previous bladder cancer (3, 17.6%), and undocumented rationale (6, 35.3%). Major postoperative complications (CDC ≥ III) did not differ significantly between groups (9.8% MMC vs 7.9% no-MMC, p = 1.0). The 24-month cumulative incidence of iVR was lower with MMC (25.0% vs 45.0%; p = 0.013). In multivariable competing-risk analysis, MMC remained independently associated with reduced iVR (subdistribution hazard ratio 0.40, 95% CI 0.20-0.78).

Intraoperative MMC instillation after bladder cuff closure achieved high institutional adherence with no significant increase in major postoperative complications and achieved a low 24-month incidence of iVR. As the comparison group was non-contemporaneous, the oncological findings are exploratory.