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

Purpose There is significant lack on evidence regarding the effect of non-adherence to a recommended protocol in follow-up of high-risk non-muscle-invasive bladder cancer (NMIBC), or the impact of delaying detection of recurrent lesion. Here, we aimed to investigate the optimal frequency of follow-up cystoscopy of high-risk NMIBC with respect to oncological safety in the Japanese real-world clinical practice. Methods This retrospective single-center study included 206 patients with primary high-risk NMIBC. The intensity (%) of follow-up cystoscopy was calculated based on actual visits for cystoscopy and guideline-recommended frequency in the first 24-month follow-up period. Inverse probability of treatment weighting analyses was used to reduce the risk of bias between groups. We performed a restricted cubic spline analysis with knots at intensity of follow-up cystoscopy ≤ 100% group to examine the possible association of progression risk with the intensity of follow-up as a continuous exposure. Results The median intensity was 87.5% (interquartile range, 75–100). Adjusted multivariate analysis for MIBC-free and progression-free survival demonstrated no significant difference between adjusted ≤ 75% and > 75% intensity groups. A restricted cubic spline analysis suggested no significant effect of the intensity of follow-up on progression risk, and hazard ratios of patients of < 100% intensity were equivalent to those of patients of 100% intensity. Conclusion Our finding suggested decreased intensity of follow-up cystoscopy did 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 existing clinical guidelines.