Bacillus of Calmette and Guerin (BCG) vaccine
Immunological Agent | Vaccine
The Bacillus Calmette-Guérin (BCG) vaccine, originally developed to prevent tuberculosis (TB), is also widely used as an intravesical immunotherapy for treating non-muscle invasive bladder cancer (NMIBC).
- Indication and Effectiveness: BCG is primarily used for treating high-grade non-muscle invasive bladder cancer, including carcinoma in situ (CIS), and for preventing the recurrence of these cancers after surgical removal (transurethral resection). It has been shown to be more effective than chemotherapy in reducing the risk of recurrence and progression.
- Mechanism of Action: When instilled directly into the bladder, BCG prompts a local immune response. This response triggers the activation of immune cells, which target and destroy residual cancer cells. The exact mechanism is not fully understood but involves the recruitment of a host of immune effectors to the bladder mucosa.
- Administration Protocol: BCG is administered via intravesical instillation, which involves the direct insertion of the vaccine into the bladder through a catheter. Typically, treatment begins several weeks post-surgery and follows a schedule like once a week for 6 weeks (induction phase), followed by maintenance therapy which might vary according to specific protocols but generally includes further instillations at decreasing frequency over 1-3 years.
- Patient Preparation and Aftercare: Patients are advised not to drink fluids for a few hours before the treatment to avoid diluting the BCG within the bladder. Post-instillation, patients are usually instructed to hold the BCG in the bladder for about 2 hours before voiding, to maximize contact time with the bladder lining. To reduce the risk of transmission and irritation, patients should thoroughly clean the toilet after voiding and may be advised to bleach the toilet.
- Managing Side Effects: Common side effects include urinary frequency, dysuria (painful urination), and hematuria (blood in urine). Flu-like symptoms such as fever, chills, and fatigue can also occur. Symptoms usually subside within 48 hours. Severe reactions, though rare, like high fever over 39°C (102.2°F) or persistent symptoms require immediate medical attention.
- Contraindications: Contraindications include traumatic catheterization, active urinary tract infection, and immunosuppression. BCG therapy is deferred until these conditions are resolved or managed to minimize risks such as systemic BCG infection.
- Monitoring and Follow-Up: Regular cystoscopy and urine cytology are performed every 3 to 6 months after BCG treatment to monitor for recurrence. The frequency of monitoring may decrease over time if no recurrences occur.
- Treatment Failure and Alternatives: In cases where BCG therapy fails or is not tolerated, options may include repeat BCG therapy with or without interferon, instillation of chemotherapy agents, or more invasive approaches such as radical cystectomy depending on the risk of disease progression and patient factors.
- Impact of BCG Shortage: Periodic shortages of BCG have challenged the management of bladder cancer globally, requiring rationing strategies such as prioritizing patients with high-risk cancer features or reducing the dose or frequency of BCG administration.
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