Bacillus Calmette Guérin in bladder cancer: is more immune stimulation better?

Intravesical instillation of bacillus Calmette Guérin (BCG) has been the therapy of choice for the treatment of high-risk non-muscle-invasive bladder cancer (NMIBC) for several decades, increasing considerably the survival of these patients. For papillary tumours, the instillations are applied as adjuvant after trans-urethral resection of the bladder (TURB); however, carcinoma in situ (CIS) cannot be excised and, in this case, BCG is used without prior surgery. Despite the advantages provided by this treatment, with around 70% of patients relapse- free after 5 years, remarkable improvements in the outcome of this therapy have not been achieved since the introduction of maintenance instillation cycles (1). This is probably related to two important facts: (I) administration of BCG varies among different hospitals, including bacterial strain, concentration and schedule; (II) the exact mechanism of action of BCG in the elimination of bladder cancer is not completely understood.