Stanford researchers have developed a urine test that can accurately predict which patients with bladder cancer will respond to standard surgery and immunotherapy treatments. In a study published in Cell, they report that this DNA test takes into account background mutations caused by aging that existing tests may otherwise mistake for cancer.
“Our test can detect minimal residual disease non-invasively after bladder cancer treatment, while accounting for mutations present in normal urothelium that have complicated prior studies,” said Joseph C. Liao, MD, professor of urology and senior author of the study. “For the first time, we were able to distinguish patients likely cured by [immunotherapy] from those cured by surgery.”
Even when detected in early stages, bladder cancer has a high relapse rate. Patients with non-muscle invasive bladder cancer (NMIBC), whose tumors are still confined to the inner layers of the bladder, are typically treated with surgery. Those with higher risk profiles are then given a bacillus Calmette Guerin (BCG) immunotherapy, which can significantly reduce recurrence risk after surgery.
However, while some patients respond well to surgery without immunotherapy, others may end up relapsing even after receiving BCG immunotherapy. Until now, there was no reliable way to predict which patients will respond to each of these treatments, making it difficult for physicians and patients alike to make informed clinical decisions.
The molecular test developed by Liao and colleagues analyzes urine tumor DNA in urine samples to detect the presence of tumor DNA and predict whether a patient will respond to standard surgery or BCG treatment. Importantly, the test was designed to account for the “field effect,” a phenomenon where even healthy people can carry cancer-associated mutations in the bladder’s lining, with these mutations becoming increasingly common as the person ages.
“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,” said William Y. Shi, MD/PhD student at Stanford School of Medicine and lead author of the study. “This allowed us to molecularly distinguish the relative contributions of surgery and BCG to disease control.”
The researchers evaluated the urine test in a cohort of 261 NMIBC patients who underwent surgery and BCG treatment. Results revealed three distinct molecular patterns of treatment response. These included surgery responders, for whom tumor DNA disappeared after surgery; BCG responders, who showed tumor DNA after surgery that was eliminated with the immunotherapy; and non-responders who saw tumor DNA levels remain stable or even increase after both treatments.
“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,” said Max Diehn, MD, PhD, professor of radiation oncology and senior author of the study.
The study also revealed distinct molecular patterns driving response to surgery and response to BCG immunotherapy. On the one hand, patients who relapsed after surgery had tumors with genetic activity linked to cell growth and invasion. On the other hand, tumors who responded to BCG had a higher mutation burden and tended to have features that made them more visible to the immune system.
Following validation in a larger patient cohort, this urine test could help spare patients who respond well to surgery from receiving an unnecessary course of immunotherapy. In particular, BCG supply has suffered from shortages for the past decade, leaving many patients waiting for longer than necessary. In the face of shortages, a predictive test could help prioritize those who are most likely to benefit from it.
For patients who are unlikely to respond to both surgery and BCG, the urine test could also prove valuable in escalating treatment early on. In the study, the test was able to identify recurrence risk in patients for whom routine cystoscopy exams appeared normal, meaning it could be able to detect relapse earlier than the current standard.
“These kinds of predictive biomarkers are critical,” said Eila C. Skinner, MD, professor of urology and chair of Stanford’s Department of Urology. “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.”
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