Toxicity data reveal no safety concerns in bladder cancer study S/N1806

Updated toxicity data from the ongoing SWOG/NRG 1806 clinical trial testing the combination of chemoradiotherapy and immunotherapy in patients with localized muscle-invasive bladder cancer reveal no significant safety concerns for the combination.

S/N1806 Study Group Member Samir G. Jawar, MD, PhD, Baylor Scott and White Health, Temple, TX, will present a safety report on 213 patients as an oral presentation at the 2022 American Society of Medicine Annual Meeting. Society for Radiation Oncology (ASTRO) in San Antonio on October 25.

Patients participating in the phase 3 S/N1806 study have non-metastatic muscle-invasive bladder cancer. All patients in the study were randomized 1:1 to one of two treatment groups. Patients in both arms are treated with standard trimodal therapy, which combines endoscopic surgery to maximally remove the bladder tumor with chemoradiation. Half of the patients in the study group also receive the immunotherapy drug atezalizumab in combination with chemoradiotherapy every three weeks for six months.

The report’s lead author is Parminder Singh, MD, a SWOG investigator at the Mayo Clinic in Phoenix, Arizona.

“This is a randomized, phase 3 clinical trial investigating the addition of immunotherapy to bladder-sparing chemoradiotherapy,” Singh said. “There are no signs of major toxicity issues in the study group, indicating the safety of the regimen, and the study continues to progress very well. If positive, the trial could lead to improved treatment options for patients with bladder cancer by which they may preserve their bladder.’

Among 213 evaluable patients, 113 received trimodality therapy and the combination of atezalizumab. The remaining 100 patients were randomized to a control group of trimodal therapy only.

Overall, 65 of 113 patients (58 percent) in the atezalizumab group reported grade 3 or higher toxicities, compared with 44 of 100 patients (44 percent) in the control group. Most of the toxicities were hematologic and not considered immune-related by the treating physician. However, a number of known side effects related to the immune system atezolizumab were registered at level 3 or higher in the study group.

A pre-specified safety analysis of the first 80 patients in the study also showed no significant increase toxicity on the experimental group compared to the control group. The S/N1806 trial continues to progress and is expected to reach its enrollment goal of 475 patients over the next two years. This is the largest study in North America examining bladder conservation therapy.

Courtesy of SWOG Cancer Research Network