Please explain BCG bladder cancer treatment.?

Immune system based. Bcg is a weakened bacteria in the family of germs that causes tuberculosis. In bladder cancer, it is believed that interactions of BCG and molecules in the cellular structure of the bladder itself induces an immune-mediated response which can cause superficial cancers of the bladder to regress and can delay or prevent recurrence in many cases. It is usually given weekly for 6 weeks to start.
Localized immune rea. Ction. If a person is immunized with BCG (a modified tuberculosis organism) re-exposure to BCG induces a local cellular immune response. If BCG is instilled into the bladder of person with bladder cancer, after prior sensitization to bcg, the local cellular immune response may destroy tumor cells.