BCG Induction Therapy in Bladder Cancer
BCG induction therapy is the initial 6-week course of intravesical Bacillus Calmette-Guérin administered to patients with high-risk non-muscle invasive bladder cancer (NMIBC) to reduce recurrence and progression rates. This treatment is the cornerstone of management for high-risk NMIBC and is advocated by both American Urological Association (AUA) and European Association of Urology (EAU) guidelines 1.
What is BCG?
BCG is a live attenuated vaccine derived from Mycobacterium bovis, originally developed for tuberculosis prevention. It was first administered to humans in 1921 2. In bladder cancer treatment, BCG works by stimulating an immune response against tumor cells when administered directly into the bladder.
BCG Induction Protocol
The standard BCG induction regimen consists of:
- Weekly intravesical instillations for 6 consecutive weeks
- Each instillation typically contains the full dose of BCG suspended in 50ml of saline
- The solution is retained in the bladder for 1-2 hours before voiding
- Complete resection of all visible tumors is essential before starting BCG therapy, especially for T1 disease 1
Efficacy of BCG Induction
BCG induction has demonstrated significant efficacy in NMIBC:
- Reduces recurrence risk by approximately 70% compared to TURBT (transurethral resection of bladder tumor) alone 1
- Response rates as high as 70% in patients with carcinoma in situ alone 1
- An estimated 50-55% of patients with high-risk NMIBC experience complete response to intravesical BCG 1
- Meta-analyses show BCG is superior to intravesical chemotherapy agents like mitomycin C for high-risk patients 1
Maintenance BCG After Induction
Level 1 evidence supports maintenance BCG therapy following successful induction:
- Maintenance BCG significantly improves recurrence-free and progression-free survival 1
- The SWOG regimen is the most validated maintenance protocol: three weekly instillations at months 3,6,12,18,24,30, and 36 1
- Median recurrence-free survival of 80 months has been reported with maintenance therapy 1
- Five-year recurrence rates of approximately 34% with BCG maintenance versus 62% with mitomycin C maintenance 1
Side Effects and Complications
BCG therapy is associated with significant side effects:
- Common local reactions: urinary frequency (71%), cystitis (67%), hematuria (23%) 1
- Systemic reactions: fever (25%) 1
- Serious complications: BCG sepsis, granulomatous prostatitis, epididymo-orchitis
- Serious local and systemic infections may require antituberculosis therapy and hospitalization 1
Patient Selection and Considerations
Not all patients are candidates for BCG therapy:
- Contraindicated in immunocompromised patients and those with active tuberculosis
- Should be delayed after traumatic catheterization or gross hematuria
- Patients with high-risk features who fail or cannot tolerate BCG may require consideration of early cystectomy 1
Quality Indicators in BCG Therapy
Guidelines suggest the following quality metrics for BCG therapy:
- 60% of eligible high-risk NMIBC patients should receive BCG induction 1
- 90% of patients with complete response to induction should receive maintenance BCG 1
BCG in Other Contexts
While this answer focuses on bladder cancer treatment, it's worth noting that BCG was originally developed as a tuberculosis vaccine and has variable efficacy (0-80%) against pulmonary tuberculosis in adults, but higher efficacy (80-100%) against serious forms of TB in children 3.
BCG is not recommended as a routine strategy for TB control in the United States 1 but may be considered in specific high-risk situations, particularly for children with continuous exposure to untreated TB 3.