Experimental Immunotherapy May Help Patients With High-Risk Bladder Cancer Avoid Bladder Removal Surgery

An international phase 3 study performed at all three Mayo Clinic destination medical centers found that a new immunotherapy helped many patients with an aggressive form of bladder cancer keep their bladder instead of having it surgically removed. The treatment also kept many patients cancer-free for more than two years and caused mostly mild side effects. The findings were published in The Lancet Oncology.

Patients in the study had high-risk bladder cancer that had returned despite standard treatment with bacillus Calmette-Guérin (BCG). For these patients, surgery to remove the bladder is typically the recommended next step. The new immunotherapy treatment, called cretostimogene grenadenorepvec, produced a complete response, with no detectable signs of cancer in 75% of patients, with many of those responses lasting beyond two years.

"Until now, patients whose cancer returned after BCG therapy have had few effective options besides bladder removal," says Mark Tyson II, M.D., lead author of the study and a urologist at Mayo Clinic in Arizona. "This study shows we may be able to offer many of those patients another option without compromising cancer control."

Among patients whose cancer completely disappeared after treatment, about 60% remained cancer-free two years later. In one patient, the cancer has not returned for more than four years after completing treatment. Most treatment-related side effects were mild, temporary bladder symptoms, and researchers reported no severe treatment-related side effects.

"For patients, this isn't just about treating cancer — it's about preserving quality of life," says Dr. Tyson. "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 study included 115 patients treated at 41 medical centers across North America, Asia and Australia. Two years after starting treatment, an estimated 81% of patients had not needed surgery to remove their bladder. The researchers concluded that cretostimogene grenadenorepvec could become an important bladder-sparing treatment option for patients whose high-risk bladder cancer has returned after standard BCG therapy. They also noted that the treatment has not been directly compared with other bladder-sparing therapies in clinical trials.

The study was funded by CG Oncology. For a complete list of authors, disclosures and funding, review the study. The therapy remains investigational.