Bladder cancer is a serious disease that begins in the lining of the bladder, the organ that stores urine.
When the cancer grows into the muscle layer of the bladder wall, it is called muscle‑invasive bladder cancer.
This form is more dangerous because it can spread to other parts of the body. For many years, the standard treatment has been surgery to remove the bladder completely, a procedure known as cystectomy.
While this surgery can save lives, it also changes daily life in major ways. Patients must use a bag to collect urine, face a higher risk of complications, and adjust to long‑term physical and emotional challenges. Because of this, many people hope to avoid bladder removal if possible.
In recent years, doctors have been studying ways to treat the cancer while keeping the bladder. New treatments that combine chemotherapy and immunotherapy before surgery have allowed some patients to respond so well that surgery might be delayed or even avoided.
However, doctors need reliable tools to decide which patients can safely keep their bladder and which ones still need surgery to prevent the cancer from spreading.
A new study from researchers at Fox Chase Cancer Center has explored whether a blood test could help guide these decisions. The test looks for circulating tumor DNA, often called ctDNA.
These are tiny pieces of genetic material released into the bloodstream when cancer cells die. By measuring ctDNA, doctors may be able to detect whether cancer is still active in the body, even when scans appear normal.
The findings come from updated results of the phase 2 RETAIN‑2 clinical trial and were presented at the 2026 ASCO Genitourinary Cancers Symposium in San Francisco.
The study was led by Dr. Pooja Ghatalia and senior author Dr. Daniel Geynisman, along with a team of clinicians. Their research focused on patients with muscle‑invasive bladder cancer who received treatment designed to preserve the bladder.
In the trial, more than seventy patients received a combination of chemotherapy and an immunotherapy drug called nivolumab before any surgery decision was made. Patients who showed a complete response to treatment entered a careful monitoring program instead of having immediate bladder removal.
After two years, most of these patients remained free from cancer spread to distant organs, suggesting that bladder‑sparing treatment can be effective for selected individuals.
Blood samples were collected at several points to measure ctDNA levels. The researchers found that patients who still had detectable ctDNA after treatment were much more likely to later develop metastasis, meaning the cancer spread to other parts of the body.
In contrast, patients with no ctDNA in their blood tended to have better outcomes, whether or not they eventually had surgery. This suggests the test may help doctors identify patients who are at lower risk and could safely avoid bladder removal.
However, the study also revealed an important limitation. Some patients developed cancer again inside the bladder, but most of these local recurrences were not detected by ctDNA testing.
This means the blood test is useful for predicting distant spread but not for finding cancer that returns in the bladder itself. Doctors will still need other monitoring methods, such as scans and direct examination of the bladder, to catch these local problems early.
The results highlight both the promise and the limits of this approach. A simple blood test could help guide treatment decisions and reduce unnecessary surgery for some patients, improving quality of life.
At the same time, it cannot replace careful follow‑up care. Researchers plan to continue tracking patients for several years and are designing a new trial to further study how ctDNA can be used in real‑world treatment planning.
In analyzing the findings, the study appears encouraging because it offers a practical way to personalize treatment based on each patient’s risk. The ability to identify who may safely keep their bladder could reduce physical and emotional burdens. However, the research is still in early stages, and the number of participants was limited.
Larger studies are needed to confirm how reliable the test is across different groups of patients. The fact that ctDNA cannot detect local recurrence also means it must be used together with other tests rather than on its own.
Overall, the study represents an important step toward more tailored cancer care, where treatment decisions are guided by biological signals from the patient’s own body.
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