Blood biomarker guides bladder-sparing treatment decisions for cancer patients

Circulating tumor DNA, or ctDNA, can predict metastatic risk in patients who receive bladder-sparing treatment for muscle-invasive bladder cancer, but it is not a good predictor of local recurrence within the bladder, according to new data presented today by Fox Chase Cancer Center researchers.

The study also showed that the absence of ctDNA predicted favorable outcomes, regardless of whether the patient's bladder was removed or not. Circulating tumor DNA are tiny fragments of DNA left behind by cancer cells as they die off during treatment.

The study, which reports updated data from the phase 2 RETAIN-2 clinical trial, could be used to help guide treatment decisions for patients with muscle-invasive bladder cancer (MIBC), said first author Pooja Ghatalia, MD, an Associate Professor in the Department of Hematology/Oncology at Fox Chase. She conducted the study with senior author Daniel M. Geynisman, MD, Chief of the Division of Genitourinary Medical Oncology, and a number of other Fox Chase clinicians.

Test can help determine treatment

"This tells us ctDNA can be incorporated into the decision-making of who should keep their bladder and who should not, knowing that we also need additional tests or biomarkers to detect local recurrence early in patients who undergo active surveillance," she said.

In addition to the findings on ctDNA, researchers also reported positive results from the trial, known as RETAIN-2, demonstrating that a response-adapted bladder-preservation approach involving neoadjuvant chemoimmunotherapy can be considered in select patients.

Safely selecting patients for bladder-sparing treatment

Keeping the bladder intact is a high priority for patients undergoing treatment for bladder cancer, Ghatalia said. Not only does bladder removal increase the risk of complications, but it also means patients must wear a urine bag for the rest of their lives, significantly affecting their quality of life.

New and better neoadjuvant therapies mean that more patients may be able to be treated for cancer without removing the bladder. However, providers need tools to better identify which patients can be safely treated with this approach and which ones still need to undergo cystectomy, a surgery to remove the bladder.

Although ctDNA has previously been shown to be an effective tool to predict outcomes in patients who have had their bladders removed, this is the first time it has been studied in patients who are treated with a bladder preservation approach.

Key findings

• Chemotherapy and immunotherapy were effective for many patients. More than 70 patients with MIBC received combination chemotherapy plus an immunotherapy known as nivolumab. Patients showing complete response entered active surveillance instead of being treated with immediate surgery. Overall, 80% of these patients remained metastasis-free after two years.
• Post-treatment ctDNA predicted metastatic risk. Blood samples were analyzed for ctDNA at multiple timepoints during the study. Patients who were ctDNA-positive after treatment were much more likely to eventually develop metastasis.
• Local recurrence was not detected by ctDNA. While the surveillance group overwhelmingly remained free of metastases, 22 patients subsequently developed a recurrence of cancer within their bladder. Of these, 19 did not show an increase in ctDNA, which means that ctDNA isn't a good way to detect local recurrences.

Looking ahead

Researchers will continue following patients from the RETAIN-2 trial for five years to study long-term outcomes of bladder-sparing treatment. They are also currently designing the RETAIN-3 clinical trial, with plans to use ctDNA as a predictive biomarker in treatment decision-making.

Ghatalia presented results of the study, "Circulating Tumor DNA (ctDNA) to Guide Response-Adapted Bladder Preservation in Muscle-Invasive Bladder Cancer (MIBC): Integrated Analysis of the RETAIN Trials," during a podium presentation at the 2026 ASCO Genitourinary Cancers Symposium, which is being held February 26-28 in San Francisco.