BCG Immunotherapy, past, present and future.

Since its introduction more than 40 years ago, adjuvant treatment with BCG (Bacillus Calmette-Guérin) for non-muscle invasive bladder cancer (NMIBC) continues to be the treatment recommended in the highrisk group, and one of the most successful immunotherapies for cancer treatment. However, up to 20% of patients will progress to muscle-invasive disease after BCG treatment. On the other hand, we are facing a shortage of BCG supply worldwide. Despite its extensive clinical use, there is no clear certainty of the mechanism of action of BCG, and controversy persists regarding to the most effective dose and strains, as well as their usefulness in combined treatments with other drugs and with devices that could facilitate their action on the bladder. This article historically reviews the impact that has had BCG in the treatment of NMIBC, the current guidelines in terms of doses, strains and treatments combination, and the future that will happen with the results of the ongoing clinical trials with systemic immunotherapy, vaccines and gene therapy.