Researchers have developed a urine-based liquid biopsy test that filters age-related mutations, potentially enabling more accurate prediction of bladder cancer recurrence and guiding immunotherapy decisions.
Researchers have developed a noninvasive urine test that uses liquid biopsy technology to determine which patients with bladder cancer are likely to benefit from immunotherapy after surgery.
The study, published in Cell from a team of investigators from the Stanford Departments of Urology and Radiation Oncology, in close collaboration with colleagues from Stanford Cancer Institute, suggests this molecular approach could help clinicians personalize treatment decisions and manage global supply shortages of common therapies.
Most patients with bladder cancer are diagnosed with non-muscle invasive bladder cancer, where tumors are confined to the inner layers of the bladder. While often detected early, the disease frequently returns. Following a transurethral resection of bladder tumor surgery, patients with high-risk features are typically recommended to receive six weekly instillations of bacillus Calmette-Guérin (BCG), an immunotherapy used to reduce the risk of recurrence.
“Our test can detect minimal residual disease non-invasively after bladder cancer treatment, while accounting for mutations present in normal urothelium that has complicated prior studies,” says Joseph Liao, MD, the Kathryn Simmons Stamey professor of urology and co-senior author of the study, in a release. “For the first time, we were able to distinguish patients likely cured by BCG from those cured by surgery.”
Filtering Background Mutations
The research team identified a biological challenge known as “clonal cystopoiesis,” where healthy individuals carry cancer-related mutations in the bladder lining that become more common with age. These non-cancerous cells can release altered DNA into urine, which can cause highly sensitive tests to mistake the mutations for active cancer. To address this, the team created a statistical method to filter out these background mutations.
“By correcting for the field effect, a known confounder of mutation-based bladder cancer detection, we improved the specificity of urine tumor DNA liquid biopsies,” says William Shi, co-lead author and an MD PhD student at Stanford School of Medicine, in a release. “This allowed us to molecularly distinguish the relative contributions of surgery and BCG to disease control.”
Three Distinct Response Patterns
The study identified three clear molecular response patterns by analyzing urine samples before surgery, after surgery, and following immunotherapy:
Surgery responders: Patients whose tumor DNA disappeared after surgery alone.
BCG responders: Patients with residual tumor DNA after surgery that decreased following immunotherapy.
Non-responders: Patients whose tumor DNA persisted or increased after BCG.
The analysis revealed that the biology driving response to surgery is different from the biology driving response to immunotherapy. Tumors resistant to surgery showed gene activity associated with cell growth and invasion, while tumors that responded to BCG had higher mutation burdens and pre-existing immune activity.
“The ability to distinguish responders from non-responders to the two treatments also allowed us to study which molecular properties make tumors more likely to benefit from each therapy,” says Max Diehn, MD, PhD, the Jack, Lulu, and Sam Willson professor of radiation oncology and co-senior author of the study, in a release.
Clinical Impact and Surveillance
The findings suggest that a field-effect-informed urine test could prioritize BCG for patients most likely to benefit, which is especially important during recurrent global shortages of the immunotherapy. In many cases, the urine test identified recurrence risk even when routine cystoscopy exams appeared normal, suggesting it may detect relapse earlier than current standard surveillance.
“These kinds of predictive biomarkers are critical,” says Eila Skinner, MD, the Thomas A. Stamey research professor of urology and chair of the department of urology, in a release. “We have new treatments that are costly and carry risk of side effects. We would love to personalize therapy to ensure each patient receives the best treatment for their individual cancer.”
