Bacillus Calmette-Guerin for the Treatment of Non-muscle Invasive Bladder Cancer: History and Current Status.

In the past decades, the bacillus Calmette-Guerin (BCG) treatment for non-muscle invasive bladder cancer, especially for intermediate and high-risk groups, is increasingly accepted by multiple guidelines. Currently, the front-line setting for the high-risk group is still intravesical BCG instillation. However, the BCG mechanism, usage, adverse events, and the definition of BCG failure are not yet fully understood or defined. In addition, despite BCG being generally efficacious, a number of bladder cancer patients are unresponsive to the BCG immunotherapy. In this review, we summarize the history and current status of BCG immunotherapy, and highlight recent developments in designing novel strategies for the treatment of BCG-unresponsive patients.