Researchers at Stanford Medicine and the VA Palo Alto Health Care System have developed a noninvasive urine test called uRARE-seq that correctly identifies 95 percent of localized bladder cancer cases. Published October 2, 2026, in Nature Medicine, the experimental assay measures cell-free RNA fragments to track tumor behavior and predict treatment responses.
How uRARE-seq Reads Tumor RNA Instead of DNA
Most liquid biopsies search for cancer-related mutations in DNA. The Stanford approach takes a different path by analyzing fragments of cell-free RNA released into urine as tumor cells grow. Because RNA reflects which genes a cancer cell is actively using, it captures tumor biology alongside the physical presence of disease, according to Stanford Medicine.
“You’re looking for a biological signature of disease, not an exact likeness, and urine is a noninvasive way to accurately detect and track bladder cancer.”
Ash Alizadeh, Moghadam Family Professor at Stanford
Normal lining cells in the bladder can accumulate mutations that overlap with those found in tumors, which can trick DNA tests. This RNA-based strategy helps bypass that known hurdle in urine testing called the field effect. Because RNA reflects broader gene activity rather than individual DNA alterations, uRARE-seq avoids that requirement while accurately distinguishing between low-grade and high-grade bladder cancer. Applied to samples from patients with bladder, kidney and prostate cancer, the resulting test closely tracked the biology of the tumors.
Testing Performance Across 683 Urine Samples
The assay outperformed standard urine cytology—where urine is examined through a microscope to identify cancerous cells—and a DNA-based test tested on the exact same sample set.
Senior author Dr. Maximilian Diehn noted the distinction between detecting a tumor’s existence and understanding its activity. Beyond initial diagnosis, the test also flagged residual disease.
Directing BCG Immunotherapy Choices
About 85,000 individuals are diagnosed with bladder cancer annually in the United States, and the disease is prone to recurrence.
The Stanford team observed that patients who subsequently had a complete molecular response to BCG showed stronger T-cell and other immune-related expression signatures. Using these patterns, the investigators constructed a biomarker model designed to predict whether a tumor is more likely to respond to immunotherapy or to chemotherapy.
“There are currently no biomarkers at all that are recommended or approved for surveillance. These treatments are incredibly taxing — physically and financially. If we can guide those choices, we have the potential to help both patients and clinicians.”
Dr. Joseph Liao, chair of the department of urology at Stanford
Moving Toward Clinical Trials
uRARE-seq is an investigational tool without regulatory approval, despite promising performance in research cohorts. The researchers plan to test it in larger, prospective, multicenter trials.
Lead author Kevin J. Liu and several coauthors hold ownership interests in Resero Bio, a Stanford spinout commercializing the technology, while senior researchers have filed related patents on urine cell-free RNA analysis.