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Objective: To assess recurrence-free survival (RFS) in patients with undetectable tumour-informed circulating tumour DNA (ctDNA) before radical cystectomy (RC) and evaluate if those who converted from detectable to undetectable ctDNA status after RC have similar RFS outcomes as those with persistently undetectable ctDNA status., Patients and Methods: Patients who underwent RC had prospectively and longitudinally collected tumour-informed ctDNA analyses during 2021-2023. ctDNA status was informed from the pre-RC specimen. The minimal residual disease (MRD) window was defined as the initial 90 days after RC. RFS was evaluated using the Kaplan-Meier method. Cox regression analysis was performed to find predictors of disease recurrence., Results: The cohort included 135 patients with 647 ctDNA analyses. The median (interquartile range [IQR]) age was 71 (63-77) years. Over a median (IQR) follow-up of 11 (7-18) months, 41 patients (30%) had a recurrence. Pre-RC undetectable ctDNA status was found in 54 patients (40%). The RFS rates at 6, 12, and 21 months were 98%, 93%, and 82%, respectively. Of 77 patients with undetectable ctDNA status at the MRD window available for conversion dynamics analysis, 43 had persistently undetectable ctDNA status (both at pre-RC and MRD window) and 31 converted from pre-RC detectable to MRD undetectable status (conversion group). The persistently undetectable group had significantly better RFS than the conversion group (log-rank, P < 0.001), with 12-month RFS rates of 97% vs 51%, and 18-month RFS rates of 88% vs 51%, respectively. On Cox multivariate analysis, only the conversion group status predicted disease recurrence., Conclusions: Patients with undetectable pre-RC ctDNA status have a favourable prognosis and may be candidates for treatment de-escalation. Those with persistently undetectable ctDNA had superior RFS compared to the conversion group. Pre-RC ctDNA status should be incorporated into trials examining ctDNA use in clinical decision-making., (© 2024 BJU International.)