Immune mechanisms in bacillus Calmette-Guerin immunotherapy for superficial bladder cancer

Purpose: Of all medical disciplines it is exclusively in urology in which immunotherapy for cancer has an established position today with intravesical bacillus Calmette-Guerin (BCG) against superficial bladder carcinoma recurrences. BCG is regarded as the most successful immunotherapy to date. However, the mode of action has not yet been fully elucidated. We provide a thorough overview of this complex field of research. Materials and Methods: Rather than simply reporting all experimental data available for better understanding the involved immune mechanisms, we chose to provide comprehensively only information supported by several independent pathways of evidence. Results: Major findings made during the last few years include systematic analyses of patient material, detailed in vitro studies and investigations in animal models, which have led to a substantially greater understanding of the mechanisms involved. Conclusions: The efficacy of BCG is based on a complex and long lasting local immune activation. The bladder as a confined compartment, in which high local concentrations of the immunotherapy agent and effective recruitment of immune cells can be achieved, serves as an ideal target organ for this type of immunotherapy approach.