BCG treatment for bladder cancer is a form of immunotherapy where a weakened strain of tuberculosis bacteria is placed directly into the bladder to trigger an immune response against cancer cells. It is the standard first-line treatment for intermediate- and high-risk non-muscle-invasive bladder cancer, the most common form of the disease. BCG stands for Bacillus Calmette-Guérin, the same organism used worldwide as a tuberculosis vaccine, repurposed here to fight cancer.
How BCG Works Against Cancer
BCG is not a chemotherapy drug. It works by waking up your immune system inside the bladder rather than directly poisoning cancer cells. When the weakened bacteria contact the bladder lining, they activate immune cells that produce inflammatory signals. This initial alarm recruits a wave of immune fighters to the area, including natural killer cells, T cells, and B cells.
The key players are a type of helper T cell that releases powerful inflammatory molecules. These molecules create an environment hostile to tumor cells. In effect, the bacteria trick your immune system into treating the bladder wall as an infection site, and the cancer cells get caught in the crossfire. This is why BCG remains so effective decades after its first use: it harnesses the body’s own defenses rather than relying on a single chemical mechanism that cancer cells can resist.
Who Is Eligible for BCG
BCG is recommended after a procedure called TURBT (transurethral resection of bladder tumor), which removes visible tumors from the bladder wall. Not every bladder cancer patient needs BCG. It is reserved for cancers that have not grown into the muscle layer of the bladder, specifically:
- High-grade early-stage tumors that sit on or just below the bladder’s inner lining
- Carcinoma in situ (CIS), a flat, high-grade cancer that spreads along the bladder surface and carries up to a 45% risk of progressing to invasive disease if left untreated
- Intermediate-risk tumors where the size, number, or recurrence pattern suggests a meaningful chance of return
If cancer has already invaded the bladder muscle, BCG is not appropriate. Those cases typically require more aggressive treatment such as bladder removal or systemic therapy.
What the Procedure Feels Like
BCG is delivered through a thin, flexible catheter inserted through the urethra into the bladder. The liquid solution containing the live bacteria is instilled directly, and then the catheter is removed. The entire office visit is usually short, though the preparation and waiting can stretch it out.
Once the solution is inside, you need to hold it in your bladder for one and a half to two hours. During this time, some clinicians suggest changing positions periodically so the solution contacts all surfaces of the bladder lining. After the holding period, you urinate to expel the solution. If your bladder naturally retains more than about two ounces of urine, your care team may drain it with a catheter after the two-hour window.
You’ll need to limit fluid intake for 6 to 10 hours before treatment and for 2 hours afterward so the solution stays concentrated inside your bladder.
The Treatment Schedule
BCG treatment happens in two phases. The first is induction: one instillation per week for six consecutive weeks. After induction, your doctor will check whether the cancer has responded, typically through cystoscopy and urine tests.
If you respond well, the second phase is maintenance. This involves three weekly instillations given at scheduled intervals: 3 months, 6 months, and 12 months after induction. For high-risk patients, maintenance continues at six-month intervals out to 36 months (three years total). That full schedule means treatments at 3, 6, 12, 18, 24, 30, and 36 months. For intermediate-risk patients, one year of maintenance is generally sufficient.
The maintenance phase is critical. Multiple large analyses have shown that BCG with maintenance significantly reduces both recurrence and progression compared to tumor removal surgery alone. Skipping maintenance sacrifices much of BCG’s long-term benefit.
Common Side Effects
Because BCG introduces live bacteria into your body, side effects are common and mostly localized to the urinary tract. Most people experience some combination of burning during urination, increased urgency, and needing to urinate more frequently. These symptoms typically start within a few hours of treatment and can last two to three days. A low-grade fever and flu-like fatigue in the first 24 to 48 hours are also normal.
Blood in the urine is common, especially in the first day or two. Joint aches and general malaise can occur as your immune system responds to the bacteria. These effects tend to be worst during the induction phase and often become more tolerable during maintenance, though some patients experience the opposite.
Rare but serious complications include a systemic infection called BCGosis, where the bacteria spread beyond the bladder. A high fever (above 101.3°F or 38.5°C) lasting more than 48 hours, severe chills, or symptoms suggesting infection in other organs warrants immediate medical attention. This is uncommon, but it is the reason BCG should never be given when there is an active urinary tract infection or visible blood from a recent biopsy, as damaged tissue allows the bacteria into the bloodstream.
Safety Precautions at Home
Because you are urinating live bacteria for several hours after treatment, you need to take specific precautions to protect household members. For six hours after each instillation, treat your urine as a biohazard.
Sit on the toilet to urinate, even if you normally stand, to minimize splashing. After each urination during that six-hour window, pour two cups of household bleach into the toilet bowl, close the lid, and let it sit for 15 minutes before flushing. Flush several times afterward. Avoid public restrooms and do not urinate outdoors during this period.
After the six-hour window, resume normal bathroom habits and increase your water intake to flush residual bacteria from your system.
What Happens if BCG Stops Working
BCG does not work for everyone, and it can stop working over time. If high-grade cancer returns within six months of completing two rounds of induction BCG (or induction plus maintenance), the cancer is classified as “BCG-unresponsive.” At that point, additional BCG is not recommended because the likelihood of a meaningful response drops substantially.
If the cancer recurs later or after only one course of BCG, a second course is reasonable. The American Urological Association guidelines specifically allow for a repeat induction in these cases before declaring BCG failure.
For BCG-unresponsive disease, several alternatives now exist. A combination of two chemotherapy agents (gemcitabine and docetaxel) given directly into the bladder has become widely adopted as an off-label option. Two newer FDA-approved therapies, a gene therapy delivered into the bladder and an engineered immune-stimulating protein combined with BCG, are also recommended for patients with carcinoma in situ that has failed BCG. An immune checkpoint inhibitor given intravenously is reserved for patients who have exhausted other bladder-sparing options, due to its broader side effect profile. Bladder removal remains the most definitive option for BCG-unresponsive high-risk disease, particularly for patients healthy enough to tolerate major surgery.
BCG Supply Challenges
BCG for bladder cancer has faced recurring global shortages over the past decade because only a small number of manufacturers produce it. The bacteria must be grown in carefully controlled conditions, and production disruptions at even one facility can affect supply worldwide. During shortages, doctors may use dose-sparing strategies, such as dividing a single vial among multiple patients, or substitute alternative intravesical regimens like the gemcitabine-docetaxel combination. If you are scheduled to begin BCG, ask your care team about current availability, as it can vary by region and institution.