Role of immunotherapy in Bacillus Calmette-Guérin unresponsive: non-muscle invasive bladder cancer.

Bacillus Calmette-Guérin (BCG) is recommended as the first-line treatment option for intermediate to high risk non-muscle invasive bladder cancer (NMIBC) by current clinical guidelines. However, despite the intravesical instillation of BCG, a significant proportion of patients with intermediate to high risk NMIBC develop intravesical recurrence. Moreover, the treatment of BCG-unresponsive NMIBC is currently challenging. There are no reliable treatment options for these patients with BCG-unresponsive NMIBC except radical cystectomy, which reported to show acceptable oncological outcomes. In this regards, reliable and safe non-invasive or less-invasive treatment options with acceptable oncological outcomes are awaited for the treatment of BCG-unresponsive NMIBC. The treatment of advanced or metastatic urothelial carcinoma has greatly advanced following the recent introduction of immunotherapeutic agents. These advancements have triggered an increasing interest in the use of immunotherapeutic agents for NMIBC, and especially for BCG-unresponsive NMIBC. The current review article aims to introduce and discuss the cutting-edge knowledge on the role of immunotherapy in BCG-unresponsive NMIBC and the currently available therapeutic strategies for its treatment. In addition, this article also summarizes the ongoing studies in this field.