Bacillus Calmette-Guérin (BCG) is an immunotherapy used to manage non-muscle invasive bladder cancer (NMIBC), which is cancer confined to the lining of the bladder. The treatment uses a weakened strain of Mycobacterium bovis to stimulate an immune response directly within the bladder. This liquid preparation is delivered via a catheter in a procedure known as intravesical instillation, where it remains in contact with the bladder wall for a specified period. The primary goal of BCG is to prevent cancer recurrence and stop the disease from progressing to deeper layers of the bladder wall.
Expected and Common Side Effects
The most common side effects of BCG therapy fall into two major categories: localized symptoms within the bladder and a temporary systemic, flu-like response. These effects are generally expected and indicate that the treatment is successfully activating the desired immune reaction. The localized bladder symptoms typically begin a few hours after the instillation and represent an inflammatory reaction in the bladder lining.
Patients frequently experience intense bladder irritation, which can manifest as urgency, or a frequent and sudden need to urinate. Dysuria, or pain and burning during urination, is also common, and mild hematuria (a small amount of blood in the urine) may occur. These symptoms are usually temporary, peaking within 24 to 48 hours after the treatment before gradually subsiding. The severity of these localized effects often increases with each subsequent instillation as the bladder becomes more sensitized.
The second category of common effects includes systemic symptoms that resemble a mild case of the flu. This can involve a low-grade fever, typically below 101.5°F, along with chills, fatigue, malaise, and generalized body aches. These symptoms are a sign that the weakened bacteria have successfully triggered a broader immune system activation. These systemic effects are usually short-lived, resolving within one to three days following the treatment session.
Practical Steps for Symptom Relief
Managing the expected side effects involves specific steps to minimize discomfort and maintain safety immediately following the instillation. After the prescribed holding time for the solution, it is important to follow post-treatment voiding protocols to limit exposure of the live bacteria to others. For the first six hours after voiding the treatment, patients should sit down to urinate to prevent splashing and then add two cups of undiluted bleach to the toilet bowl, waiting 15 to 20 minutes before flushing.
Increasing fluid intake by drinking plenty of water after the first few voids helps to flush the residual BCG from the system. This also dilutes the urine, which may lessen the painful burning sensation. For flu-like symptoms, over-the-counter pain relievers such as acetaminophen are often recommended to control low-grade fever and body aches. It is advisable to take these medications only after the instillation to ensure the fever is low-grade and not a sign of a more serious issue.
If bladder spasms or severe cramping occur, a physician may prescribe antispasmodic medication to relax the bladder muscle and reduce the intensity of the urgency and pain. General self-care strategies, such as resting on the day of treatment and the day after, can also significantly improve tolerance of the temporary fatigue and malaise. These measures help patients continue the full course of treatment.
Identifying Rare and Severe Complications
While the common side effects are manageable, patients must be aware of the rare possibility of severe systemic complications that require immediate medical attention. The most significant of these is disseminated BCG infection, often called BCGitis, which occurs when the bacteria spread beyond the bladder into the bloodstream. This is a severe infectious condition.
Signs of this serious complication include a high and persistent fever, typically above 103°F, that lasts for more than 48 hours and does not respond to standard fever-reducing medication. Other indicators of a severe systemic reaction include symptoms of sepsis, such as confusion, a rapid heart rate, or lethargy. Disseminated infection can also cause inflammation in other organs, presenting as persistent joint pain or a severe cough and shortness of breath due to pneumonitis.
Although rare, occurring in less than one percent of patients, these severe reactions demand immediate contact with the oncology team or an emergency room visit. Prolonged localized symptoms, such as painful urination or blood in the urine that lasts for weeks rather than days, also warrant a medical evaluation to rule out a persistent infection or other complications. Prompt intervention with specific anti-mycobacterial therapy is necessary to manage these severe adverse events.