Use of the Connaught strain of bacillus Calmette-Guérin, an adjuvant immunotherapy used in the treatment of non-muscle-invasive bladder cancer, significantly reduced cancer recurrence compared with the Tice strain of bacillus Calmette-Guérin, the data revealed.
Cyrill A. Rentsch, M.D., Ph.D., of the division of urology at the University of Basel in Switzerland, presented the phase III data, which represent the potential for a shift in the standard-of-care treatment for non-muscle-invasive bladder cancer.
Bacillus Calmette-Guérin (BCG) was originally developed as a vaccine for tuberculosis but has also been the standard of care for the treatment of noninvasive bladder cancer for more than 30 years. Currently, at least eight strains of BCG are used in treating bladder cancer.
"This is the first study demonstrating that different BCG strains lead to different clinical outcomes in the treatment of bladder cancer," Rentsch said.
He and his colleagues prospectively compared the efficacy of the Connaught and Tice strains in preventing recurrences and progression of cancer. They recruited and randomly assigned 149 patients to six weekly injections of Tice or Connaught. All patients had undergone surgery to remove visible bladder tumors.
After a median follow-up of 25 months, the five-year recurrence-free survival rate for all patients was 61 percent. Patients who underwent treatment with Connaught had significantly fewer recurrences compared with patients treated with Tice. The five-year recurrence-free survival for patients treated with Connaught was 75 percent compared with 46 percent for patients treated with Tice.
"At five years, this results in a more than twofold improvement in the recurrence rate in favor of BCG Connaught," Rentsch said. "Based on its common use, we estimate that more than 20 percent of the worldwide population is at risk to receive treatment with BCG Tice, a treatment that, based on our findings, is less effective in reducing recurrences than BCG Connaught."
These results have the potential to substantially improve the course of disease in many patients with non-muscle-invasive bladder cancer, according to Rentsch.
"As an example of clinically successful immunotherapy, it is a must to further dissect and understand the specific mechanisms underlying BCG immunotherapy," Rentsch said. "The genetic differences identified between the two strains might represent a start for further studies."