Theories behind Bacillus Calmette-Guérin failure in high-risk non-muscle-invasive bladder cancer and update on current management

Bladder cancer encapsulates a wide spectrum of disease severities, with non-muscle invasive bladder cancer (NMIBC) representing an entirely different entity from muscle-invasive disease. Bacillus Calmette-Guérin (BCG) is one of the most successful intravesical treatment methods for patients diagnosed. However, a considerable proportion of patients fail to respond to BCG treatment. Given the propensity for recurrence in patients with high-risk bladder cancer, these patients present with surgical dilemmas. There is currently no gold standard for salvage treatment post-BCG failure or unified definition as to what that means. In this review, we discuss the mechanisms of action and pathophysiology of BCG, potential theories behind BCG failure, and the scope of novel treatments for this surgical conundrum.