Biomarkers

Urinary Biomarkers Move Closer to Clinical Use in Bladder Cancer

Urinary biomarkers have long been investigated as a less invasive way to support bladder cancer detection and surveillance, but translating promising molecular signals into routine clinical practice remains challenging. A recent narrative review highlights why bladder cancer may be particularly well suited to this approach: malignant urothelium is in direct contact with urine, allowing tumor cells, DNA, RNA, proteins, extracellular vesicles, and immune signals to enter the urinary compartment. This creates opportunities to obtain information about tumor biology through a specimen that can be collected repeatedly and noninvasively.

For urologists, one of the most immediate potential applications is helping determine which patients require invasive evaluation. Cystoscopy remains central to bladder cancer diagnosis and surveillance, while urine cytology continues to provide high specificity for high-grade urothelial carcinoma and carcinoma in situ but has lower sensitivity for low-grade tumors. Newer mutation-, methylation-, and transcript-based urinary assays could potentially provide additional information for hematuria evaluation and recurrence surveillance. Importantly, the authors emphasize that these tests should currently be viewed as decision-support or triage tools rather than replacements for cystoscopy.

Urinary molecular testing may also provide insight following transurethral resection of bladder tumor (TURBT). Tumor-informed urinary DNA is particularly interesting because persistence of patient-specific tumor alterations after an apparently complete resection could indicate residual clonal disease. The timing of testing, however, is critical. Urine collected immediately after TURBT may contain molecular material released by bleeding, tissue disruption, inflammation, or nonviable tumor cells. A tumor-associated signal that persists after an appropriate recovery period, or reappears after initially clearing, may carry greater clinical significance than an isolated positive result shortly after the procedure.

Surveillance and BCG-response monitoring represent additional areas of investigation. Serial mutation and methylation testing has shown the potential to identify molecular changes before recurrence becomes visible on cystoscopy, although a positive molecular test with negative cystoscopy does not necessarily confirm recurrent disease. During BCG therapy, interpretation becomes even more complex because treatment intentionally produces a local immune response. Changes in urinary cytokines or immune-cell signals may demonstrate biological engagement with BCG, but inflammation alone cannot establish tumor clearance. Combining immune-response markers with tumor-informed molecular signals may ultimately provide a more complete picture of treatment activity.

The emerging evidence suggests that urinary biomarkers may eventually help urologists answer more specific clinical questions, from identifying patients who need closer surveillance to recognizing persistent disease after treatment. However, the review cautions against using urinary results in isolation to drive major treatment decisions such as repeat TURBT, treatment escalation, or radical cystectomy. Cystoscopy, pathology, cytology, imaging, and established clinicopathological risk factors remain essential. The next step for urinary biomarkers is therefore not simply demonstrating that they can detect bladder cancer, but establishing when their results can safely and meaningfully change patient management.