BCG therapy is a form of immunotherapy that uses a weakened strain of tuberculosis bacteria to trigger your immune system into attacking bladder cancer cells. It’s the standard treatment for non-muscle-invasive bladder cancer (NMIBC), the most common form of the disease, and it reduces tumor recurrence by roughly 40% compared to surgery alone. The treatment is delivered directly into your bladder through a catheter, making it a localized therapy rather than a whole-body treatment like traditional chemotherapy.
How BCG Works Against Cancer
BCG stands for Bacillus Calmette-Guérin, a live but weakened form of the bacterium that causes tuberculosis. It was originally developed as a tuberculosis vaccine and has been used against bladder cancer since the 1970s. When placed directly into the bladder, BCG bacteria attach to and enter both normal bladder lining cells and cancer cells. This triggers the cancer cells to release immune signaling molecules that essentially call for backup.
Your immune system responds aggressively to the foreign bacteria and, in the process, targets the cancer cells harboring them. Multiple types of immune cells get involved: T cells, natural killer cells, white blood cells called granulocytes, and macrophages that engulf foreign material. These cells kill bladder cancer in several ways, including direct cell-to-cell destruction and by releasing proteins that force cancer cells into programmed death. The cancer cells themselves also play a role by presenting bits of bacterial and tumor material to immune cells, effectively painting a target on themselves.
Who Receives BCG Therapy
BCG is used for bladder cancers that haven’t grown into the muscle wall of the bladder. Nearly all patients first undergo a procedure called transurethral resection (TUR), where a surgeon removes visible tumors through the urethra. BCG comes afterward to destroy any remaining cancer cells and reduce the chance the cancer comes back.
How aggressively BCG is used depends on your cancer’s risk level. For intermediate-risk cancers, such as slow-growing tumors that have recurred within a year or a single fast-growing early-stage tumor, BCG is one of several options alongside intravesical chemotherapy drugs. For high-risk cancers, including large high-grade tumors, fast-growing stage I tumors, and carcinoma in situ (flat, high-grade cancer that spreads along the bladder lining), BCG is the preferred treatment. If BCG fails in high-risk patients, options include other immunotherapy drugs, intravesical chemotherapy, or surgical removal of part or all of the bladder.
What the Treatment Schedule Looks Like
BCG treatment starts with an induction phase: one instillation per week for six weeks. After that, most patients move into a maintenance phase with treatments roughly once a month for at least 6 to 12 months. For high-risk cancers, maintenance can continue for up to three years. Intermediate-risk patients typically receive up to one year of maintenance.
Each session follows a similar routine. A nurse or doctor inserts a thin catheter through your urethra into your bladder and injects the liquid BCG solution. You then hold the solution in your bladder for two hours. After two hours, you urinate it out. The entire clinic visit is relatively quick, though the two-hour holding period can feel uncomfortable, especially if you already have bladder irritation from previous treatments.
Bathroom Safety After Treatment
Because BCG contains live bacteria, you need to follow specific hygiene steps for six hours after each treatment. These precautions protect household members and anyone who might come into contact with your urine.
- Bleach your toilet: After urinating, add two cups of household bleach to the toilet bowl, close the lid, and wait 15 minutes before flushing.
- Wash thoroughly: Clean your hands, inner thighs, and genital area with soap and water every time you use the bathroom.
- Sit to urinate: This limits urine splash onto surfaces.
- Handle clothing carefully: If urine gets on clothing, wash it immediately and separately from other laundry.
- Avoid public restrooms and do not urinate outdoors during the six-hour window.
- Incontinence pads: If you use one, pour bleach on the pad, let it soak in, then seal it in a plastic bag before placing it in the trash.
How Effective BCG Is
A large meta-analysis of randomized trials found that about 40.5% of patients treated with BCG experienced tumor recurrence, compared to 49.7% of patients who did not receive BCG. That translates to a statistically significant reduction in recurrence risk. The benefit was even more pronounced when patients completed a full maintenance course rather than just the six-week induction, and in patients with papillary carcinoma (tumors that grow in finger-like projections from the bladder wall), where BCG cut recurrence odds roughly in half.
These numbers underscore why maintenance therapy matters. Stopping after the initial six weeks leaves a meaningful amount of benefit on the table. The full course, whether one or three years, provides the strongest protection against the cancer returning.
Common Side Effects
Side effects are common with BCG, though most are local and manageable. In a large European study of over 1,300 patients, about 63% reported local side effects and 31% had some degree of systemic (whole-body) effects. The most frequent local complaints were bladder irritation resembling a urinary tract infection (35%), the urge to urinate more than once per hour (24%), visible blood in the urine (23%), and actual bacterial urinary infections (23%). Systemically, general malaise hit about 16% of patients and fever about 8%.
One reassuring finding: side effects don’t necessarily get worse over time. The frequency of symptoms was similar during the initial six-week induction, the first year of maintenance, and the following two years. Reactions are more about individual biology than cumulative exposure. Some people tolerate treatment well throughout, while others have strong reactions from the very first session.
Serious Complications
Severe reactions to BCG are rare but can be serious. The most concerning is systemic BCG infection, sometimes called BCGosis, where the live bacteria spread beyond the bladder. This can cause high fever (above 103°F), pneumonia-like lung inflammation, liver inflammation, joint pain, and in rare cases, sepsis. These systemic events are more common within the first three months of treatment but can occasionally appear months or even years later.
Other serious complications include inflammation of the prostate, infection of the epididymis (a tube near the testicle), bladder contracture, and kidney abscess. Because of these risks, BCG is not given to patients with visible blood in their urine, after a traumatic catheter insertion, or within 7 to 14 days of any bladder or prostate surgery. Total bladder incontinence is also a contraindication since the patient can’t retain the solution long enough for it to work. Anyone who has had a serious adverse reaction to a previous BCG treatment should not receive it again.
BCG Supply Shortages
BCG for bladder cancer has faced ongoing supply constraints. Only one manufacturer, Merck, produces the intravesical form (Tice BCG) used in the United States and many other countries. Increased global demand has outpaced production capacity, and the drug has been placed on allocation, meaning hospitals receive limited quantities based on available inventory rather than full orders.
This shortage has forced urologists to make difficult rationing decisions. Several urology associations have published guidelines recommending strategies like reducing doses, prioritizing high-risk patients for full treatment courses, and using alternative intravesical chemotherapy agents for lower-risk patients who might otherwise have received BCG. The FDA has also authorized an expanded access program for a recombinant (lab-engineered) version of BCG from ImmunityBio, Inc. It’s worth noting that the BCG vaccine given for tuberculosis prevention is not the same product and cannot be substituted for the intravesical cancer treatment.