For patients with a aggressive type of bladder cancer that keeps coming back, surgery to remove the bladder has often been the only option. But a major new study offers a different path forward.
Researchers at Mayo Clinic in Arizona led an international study testing a new immunotherapy drug called cretostimogene grenadenorepvec. The treatment works by injecting a modified virus directly into the bladder, where it helps the immune system recognize and attack cancer cells. The phase 3 study followed 115 patients at 41 medical centers across North America, Asia, and Australia. All of these patients had high-risk bladder cancer that had returned despite standard treatment with BCG therapy, a common first-line approach.
The results were striking. Among patients receiving the new immunotherapy, 75% experienced a complete response — meaning no detectable signs of cancer remained. Many of those responses held strong for more than two years. For patients whose cancer completely disappeared after treatment, about 60% remained cancer-free two years later. In one remarkable case, the cancer has not returned for more than four years since completing treatment.
Perhaps most importantly, the treatment helped most patients avoid surgery altogether. Two years after starting the immunotherapy, an estimated 81% of patients had not needed their bladder removed.
Dr. Mark Tyson II, a urologist at Mayo Clinic in Arizona and the study's lead author, noted that this marks a real shift for patients who previously had few choices. "Until now, patients whose cancer returned after BCG therapy have had few effective options besides bladder removal," Tyson said. "This study shows we may be able to offer many of those patients another option without compromising cancer control."
The treatment also showed a favorable safety profile. Most side effects were mild, temporary bladder symptoms such as frequent urination or mild discomfort. Researchers reported no severe treatment-related side effects.
"For patients, this isn't just about treating cancer — it's about preserving quality of life," Tyson said. "Avoiding bladder removal can have a profound impact on daily living. Seeing patients remain cancer-free for years while keeping their bladder is exactly the outcome we've been hoping to achieve."
The findings, published in The Lancet Oncology, suggest that cretostimogene grenadenorepvec could become an important option for patients whose high-risk bladder cancer has returned after standard therapy. The researchers noted that while the results are promising, the treatment has not yet been directly compared with other bladder-sparing therapies in clinical trials.
Still, for thousands of patients facing the prospect of major surgery, this research points toward a future where keeping their bladder doesn't mean sacrificing their chance to beat cancer.