Monitoring of plasma and urine tumor-derived DNA to inform bladder-sparing approaches for patients with muscle-invasive bladder cancer.

We previously reported initial results from a clinical trial testing a strategy in which patients with muscle-invasive bladder cancer (MIBC) achieving a clinical complete response after cystoscopic resection of the bladder tumor plus systemic therapy could forgo removal of their entire bladder (cystectomy). While the results were highly promising, a subset of patients omitting initial cystectomy developed recurrence highlighting the need for biomarkers to refine selection of patients for this approach. We here report long-term follow-up of these patients and investigate whether tumor DNA in the plasma (ctDNA) or urine (utDNA) could inform prognosis and the need for cystectomy. Three-year bladder-intact survival among patients with a complete clinical response following four rounds of systemic therapy was 69%. Metastatic risk was significantly higher for patients with detectable versus undetectable ctDNA pre-systemic therapy (HR 4.68; 95% CI 1.10-43.35; log-rank p=0.036). Only 4.5% of patients with undetectable baseline ctDNA developed metastatic disease. Undetectable ctDNA before or after systemic therapy was associated with extremely low metastatic risk. Urine utDNA was more sensitive than plasma ctDNA at detecting residual disease within the bladder, and detectable urine utDNA in patients with a complete clinical response was associated with shorter bladder-intact survival (HR 6.47, 95% CI 1.34-31.31; log-rank p=0.008). These findings establish the conceptual and experimental foundation for incorporating ctDNA and utDNA assays into the management of patients with MIBC, particularly with respect to the need for cystectomy.