BCG (Bacillus Calmette-Guerin) treatment is a type of immunotherapy used to treat early-stage bladder cancer, including non-muscle invasive bladder cancer (NMIBC) and carcinoma in situ (CIS) . It is administered by injecting a liquid drug directly into the bladder through a catheter, which helps "turn on" the immune system cells in the bladder, which then attack the bladder cancer cells. BCG treatment is usually given once a week for six weeks, starting 2-4 weeks after transurethral resection of bladder tumor (TURBT) surgery. If the body responds to the treatments, more sessions may be scheduled. BCG treatment is the most effective treatment for early-stage bladder cancer when performed in combination with TURBT. It can slow tumor growth and reduce the chance of needing a cystectomy in the future. However, BCG treatment is not effective against bladder cancer that has metastasized (spread to other parts of the body) . Some potential side effects of BCG treatment include a small amount of blood in the urine, bladder irritation, and flu-like symptoms. For most people with high-risk NMIBC, the initial course of six BCG treatments is followed by maintenance BCG, which can last for 1-3 years.