Fox Chase Cancer Center investigators reported phase 2 RETAIN‑2 results showing that a blood‑based circulating tumor DNA (ctDNA) test can identify muscle‑invasive bladder cancer patients at low metastatic risk who may safely avoid immediate radical cystectomy. The trial used ctDNA as a predictive biomarker to stratify post‑treatment surveillance and preservation approaches. Investigators said ctDNA‑negative patients had low rates of subsequent metastasis, supporting ctDNA as a decision tool for bladder preservation strategies. The study highlights ctDNA’s expanding role beyond detection into treatment‑deintensification and personalized surgical decision making. If validated in larger cohorts, the assay could alter standard care by sparing select patients from morbid surgery and focusing aggressive interventions on ctDNA‑positive high‑risk cases.