Delaying BCG immunotherapy onset after transurethral resection of non-muscle-invasive bladder cancer is associated with adverse survival outcomes

Purpose This study was carried out to assess whether a prolonged time between primary transurethral resection of non-muscle-invasive bladder cancer (TURB) and implementation of bacillus Calmette–Guerin (BCG) immunotherapy (time to BCG; TTBCG) is associated with adverse oncological survival in patients with T1 high-grade (HG) non-muscle-invasive bladder cancer (NMIBC). Materials and methods Data on 429 patients from 13 tertiary care centers with primary T1HG NMIBC treated with reTURB and maintenance BCG between 2001 and 2019 were retrospectively reviewed. Change-point regression was applied following Muggeo’s approach. The population was divided into subgroups according to TTBCG, whereas the recurrence-free survival (RFS) and progression-free survival (PFS) were estimated with log-rank tests. Additionally, Cox regression analyses were performed. Due to differences in baseline patient characteristics, propensity-score-matched analysis (PSM) and inverse-probability weighting (IPW) were implemented. Results The median TTBCG was 95 days (interquartile range (IQR): 71–127). The change-point regression analysis revealed a gradually increasing risk of recurrence with growing TTBCG. The risk of tumor progression gradually increased until a TTBCG of approximately 18 weeks. When the study population was divided into two subgroups (time intervals: ≤ 101 and > 101 days), statistically significant differences were found for both RFS (p = 0.029) and PFS (p = 0.005). Furthermore, in patients with a viable tumor at reTURB, there were no differences in RFS and PFS. After both PSM and IPW, statistically significant differences were found for both RFS and PFS, with worse results for longer TTBCG. Conclusion This study shows that delaying BCG immunotherapy after TURB of T1HG NMIBC is associated with an increased risk of tumor recurrence and progression.