Impact of timing of adjuvant chemotherapy following radical cystectomy for bladder cancer on patient survival

{Background: Trials of adjuvant chemotherapy following radical cystectomy generally require chemotherapy to start within 90 days postoperatively. However, it is unclear, whether the interval between surgery and start of adjuvant therapy (S-AC-interval) impacts the oncological outcome. Methods: Using the Retrospective International Study of Invasive/Advanced Cancer of the Urothelium (RISC) data base, we identified patients who underwent radical cystectomy for muscle invasive bladder cancer and subsequent adjuvant chemotherapy. Univariate analysis of patient characteristics, surgical factors and tumor characteristics regarding their impact on S-AC-interval was performed using Kruskal-Wallis testing and Fisher's exact test. Analysis of progression-free (PFS) and overall survival (OS) (follow-up time beginning with the start date of adjuvant chemotherapy) was analyzed in relation to S-AC-interval (continuous and dichotomous with a cut-off at 90 days) using Kaplan-Meier method and COX regression analysis. Results: We identified 238 eligible patients (83.5% male, mean age: 63.4 years, 76.1% T3/T4, 66.4% pN+, 14.7% R+, 70.6% urothelial carcinoma, 71% cisplatin-based adjuvant chemotherapy). The majority of patients (n = 207, 87%) started chemotherapy within 90 days after surgery. Median S-AC-interval was 57 days (interquartile range 32.8). S-AC-interval did not have consistent association with any patient/tumor characteristics or surgery related factors (type of surgery, urinary diversion). Survival analysis using continuous S-AC-interval revealed a trend toward an impact of S-AC-interval on OS (hazard ratio 1.004, 95% confidence ratio 0.9997-1.0084