Genetic and immunologic determinants of intravesical BCG therapy in non-muscle-invasive urothelial bladder cancer

Bladder cancer (BCA) is one of the most common cancers. In 2010 in Poland, 6296 people developed bladder cancer and 3110 people died of it. Immunotherapy with BCG (Bacillus Calmette-Guérin) is by far the most effective adjuvant therapy. Noninfiltrating muscle membrane changes, that is, stages Ta, Tis and T1 qualify for BCG immunotherapy. BCG immunotherapy comprises series of bladder instillations, containing attenuated strain of Mycobacterium bovis. The effectiveness of immunotherapy in non-invasive bladder cancer is 70% 5-year survival without recurrence of the tumor. The treatment leads to a reduction of the residual tumor mass, but also to the delay and/or prevention of relapse, disease progression and ultimately death. Cytokines, as key mediators of immune response, play an important role in the pathogenesis of bladder cancer, which occurrence is stimulated by the inflammatory process. BCG immunotherapy provokes an intensive immunological response by the increase of cytokine production. Genetic variants determine inter-individual differences in the incidence of this cancer, as well as the response to the therapy. This is evidenced by the presence of differences in genetic variants of cytokines correlated with the varied risk of bladder cancer incidence. It is believed that concentrations of particular cytokines in urine after installation of BCG may indicate response to the therapy. Increased levels of Th1 cytokines - IFN-γ, IL-2 and TNF-α are correlated with longer survival time without recurrence, whereas high levels of Th2 cytokines such as IL-10, predict unsuccessful BCG therapy.