Bacillus Calmette-Guérin (BCG) instillation is a highly effective immunotherapy used to treat Non-Muscle-Invasive Bladder Cancer (NMIBC). This cancer is confined to the inner lining of the bladder and has not grown into the muscle layer. Intravesical therapy, which delivers the treatment directly into the bladder, is the standard of care for patients at intermediate or high risk of recurrence or progression. BCG is considered the most successful microbial immunotherapy currently available for reducing the likelihood of the cancer returning.
How BCG Triggers an Immune Response
BCG is a form of immunotherapy that harnesses the body’s defense system to fight cancer cells, unlike traditional chemotherapy. The solution contains a live, but weakened, strain of the bacterium Mycobacterium bovis, a close relative of the bacteria that causes tuberculosis. This weakened bacteria is instilled into the bladder to provoke a powerful, localized inflammatory reaction on the bladder lining, rather than causing a systemic infection.
The presence of BCG activates both the innate and adaptive arms of the immune system within the bladder. This inflammation recruits various immune cells, including T-cells, macrophages, and natural killer cells. These cells recognize the BCG and become activated to attack any lingering bladder cancer cells. The immune cells release signaling proteins called cytokines, which amplify the anti-tumor response. This targeted, immune-mediated destruction of cancer cells prevents tumor recurrence and progression.
The Treatment Schedule and Administration Process
BCG treatment is administered directly into the bladder via intravesical instillation. Patients are advised to restrict fluid intake for several hours beforehand to concentrate the urine. The procedure begins with the patient emptying their bladder completely.
A thin, flexible catheter is temporarily inserted through the urethra into the bladder. The liquid BCG solution is slowly instilled through this catheter. Once the solution is in place, the catheter is removed, and the patient retains the fluid for approximately one to two hours to maximize contact time with the bladder lining.
The initial phase is induction therapy, consisting of one instillation per week for six consecutive weeks. Patients who respond well then receive maintenance therapy to sustain the anti-cancer effect and prevent recurrence. Maintenance schedules vary but typically involve three weekly treatments given periodically over one to three years.
After the retention period, specific precautions are necessary when voiding the fluid due to the presence of live, weakened bacteria. Patients must sit while urinating to minimize splashing. The voided urine must be disinfected by adding an equal volume of household bleach to the toilet bowl and allowing it to sit for about 15 minutes before flushing.
Managing Common Treatment Reactions
Patients will experience a range of side effects, which often signal that the immune system has been successfully activated. Localized side effects within the bladder are common and include symptoms similar to a urinary tract infection, known as BCG cystitis. Patients frequently report increased urgency and frequency of urination, and dysuria (a burning or painful sensation during voiding).
Hematuria, or blood in the urine, is another common local reaction occurring shortly after instillation. These bladder symptoms are most pronounced for the first 24 to 72 hours after treatment and usually subside on their own. Mild pain relievers and maintaining good hydration are generally sufficient to manage this discomfort.
Systemic reactions, indicating a body-wide immune response, can also occur. Many patients experience transient flu-like symptoms, including chills, fatigue, malaise, and a low-grade fever that is usually below 101°F. These systemic effects also tend to resolve within two to three days after treatment.
Patients must be aware of the signs of a serious systemic infection, which is a rare but serious complication. If a patient develops a high fever (over 101.5°F) or if flu-like symptoms persist beyond 72 hours, they must contact their doctor immediately. Persistent, severe pain or signs of severe systemic illness require immediate medical attention to rule out a disseminated BCG infection, which may require specific antituberculosis medication.
Monitoring Treatment Success
Assessing the effectiveness of BCG instillation involves ongoing surveillance to detect any signs of recurrence. The primary monitoring method is regular cystoscopy, where a doctor uses a small camera to look inside the bladder. Cystoscopy is performed every few months, especially during the first two years following treatment.
If suspicious areas are seen during the cystoscopy, biopsies are taken for microscopic examination to confirm if cancer cells remain. This rigorous follow-up schedule is necessary because non-muscle-invasive bladder cancer has a tendency to recur, even after successful treatment. The goal is to identify new or returning tumors early while they are still treatable with local therapy.
If the cancer recurs despite BCG instillation, or if the disease progresses to a higher stage, it is categorized as BCG failure. Alternative treatment strategies are then discussed, which may include different intravesical agents or, for high-risk progression, a radical cystectomy (surgical removal of the bladder). The long-term monitoring ensures that any necessary changes in the treatment plan are made promptly.