Prognostic effect of the intensity of follow-up cystoscopy in patients with high-risk non-muscle invasive bladder cancer

Abstract Background There is a significant lack of evidence regarding the effect of non-adherence to recommended protocols in the follow-up of high-risk non-muscle-invasive bladder cancer (NMIBC) or the impact of delayed detection of recurrent lesions. Here, we investigated the optimal frequency of follow-up cystoscopy for high-risk NMIBC concerning oncological safety in a real-world Japanese clinical practice. Methods This retrospective, single-center study included 206 patients with high-risk primary NMIBC. The intensity (%) of follow-up cystoscopy was calculated based on actual cystoscopy visits and the recommended frequency in the first 24-month follow-up period. The inverse probability of treatment weighting analysis was used to reduce the risk of bias between the groups. We performed restricted cubic spline analysis with knots at the intensity of follow-up cystoscopy ≤ in the 100% group to examine the possible association between progression risk and the intensity of follow-up as a continuous exposure. Results The median intensity was 87.5% (interquartile range, 75%−100%). The adjusted multivariate analysis of MIBC-free and progression-free survival demonstrated no significant differences between the adjusted ≤75% and > 75% intensity groups. Restricted cubic spline analysis suggested no significant effect of follow-up intensity on progression risk, and the hazard ratios of patients with < 100% intensity were equivalent to those of patients with 100% intensity. Conclusion Our findings suggest that decreased intensity of follow-up cystoscopy does not affect oncological outcomes in patients with high-risk NMIBC. Further prospective trials directly aimed at investigating optimized follow-up schedules for NMIBC are mandatory before substantial changes to the existing clinical guidelines are made.