Survival Outcomes After Immediate Radical Cystectomy Versus Conservative Management with Bacillus Calmette-Guérin Among T1 High-grade Micropapillary Bladder Cancer Patients: Results from a Multicentre Collaboration

Background: Literature lacks clear evidence regarding the optimal treatment for non-muscle-invasive micropapillary bladder cancer (MPBC) due to its rarity and the presence of only small sample size and single-centre studies. Objective: To assess cancer-specific mortality (CSM) and overall mortality (OM) between immediate radical cystectomy (RC) and conservative management among T1 high-grade (HG) MPBC. Design, setting, and participants: We retrospectively analysed a multicentre dataset including 119 T1 HG MPBC patients treated between 2005 and 2019 at 15 tertiary referral centres. The median follow-up time was 35 mo (interquartile range: 19-64). Intervention: Patients underwent immediate RC versus conservative management with bacillus Calmette-Guérin. Outcomes measurements and statistical analysis: Cumulative incidence functions and Kaplan-Meier methods were applied to estimate survival outcomes. Multivariable Cox analyses were performed to assess independent predictors of disease recurrence and disease progression after conservative management; covariates consisted of pure MPBC, concomitant lymphovascular invasion (LVI), and carcinoma in situ at initial diagnosis. Results and limitations: Immediate RC and conservative management were performed in 27% and 73% of patients, respectively. CSM and OM did not differ significantly among patient treated with immediate RC versus conservative management (Pepe-Mori test p = 0.5 and log-rank test p = 0.9, respectively). Overall, 66.7% and 34.5% of patients experienced disease recurrence and disease progression after conservative management, respectively. At multivariable Cox analyses, concomitant LVI was an independent predictor of disease recurrence (p = 0.01) and progression (p = 0.03), while pure MPBC was independently associated with disease progression (p = 0.03). The absence of a centralised re-review and the retrospective design represent the main limitations of our study. Conclusions: Conservative management could achieve satisfactory results among T1 HG MPBC patients with neither pure MPBC nor LVI at initial diagnosis. Patient summary: Bacillus Calmette-Guérin seems to be an effective therapy for T1 micropapillary bladder cancer patients with neither pure micropapillary disease nor lymphovascular invasion at initial diagnosis.