BCG a live attenuated form of Mycobacterium bovis

Mycobacterium bovis

Mycobacterium bovis is a slow-growing , aerobic bacterium and the causative agent of tuberculosis in cattle...

, is the most commonly used agent for intravesical therapy. A number of other intravesical agents have been compared to BCG, but none has proved consistently superior.

Although the exact mechanism of its antitumor action is unknown, intravesical instillation of BCG triggers a variety of local immune responses which appear to correlate with antitumor activity. Hence it is considered an immunotherapy

Immunotherapy

Immunotherapy is a medical term defined as the "treatment of disease by inducing, enhancing, or suppressing an immune response". Immunotherapies designed to elicit or amplify an immune response are classified as activation immunotherapies. While immunotherapies that reduce or suppress are...

.

Intravesical BCG is the most efficacious agent for superficial bladder cancer

Bladder cancer

Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...

. BCG therapy has been shown to delay (although not necessarily prevent) tumor

Tumor

A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

 progression to a more advanced stage, decrease the need for subsequent cystectomy

Cystectomy

Cystectomy is a medical term for surgical removal of all or part of the urinary bladder. It may also be rarely used to refer to the removal of a cyst, or the gallbladder. The most common condition warranting removal of the urinary bladder is bladder cancer. After the bladder has been removed, an...

, and improve overall survival.