What is the mechanism of action of Bacillus Calmette-Guérin (BCG) immunotherapy for bladder cancer?

Updated: Nov 12, 2019
  • Author: Gary David Steinberg, MD, FACS; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Answer

Answer

The mechanism of action of BCG therapy is incompletely understood. Some early studies purported that an immune response against bacillus Calmette-Guérin (BCG) surface antigens cross-reacted with putative bladder tumor antigens, and this was proposed as the mechanism for the therapeutic effect of BCG; however, multiple subsequent studies refute this claim.

Once in the bladder, the live organisms enter macrophages, where they induce the same type of histologic and immunologic reaction as found in patients with tuberculosis. BCG vaccine also has been shown to have a predilection for entering bladder cancer cells, where the proteins are broken down and fragments are combined with histocompatibility antigens and displayed on the cell surface. This induces a cytokine and direct cell-to-cell cytotoxicity response, which targets these cells for destruction.

The overall response to BCG is limited if the patient is immunosuppressed.

Dal Moro and collegues evaluated the influence of hypertension on the outcome of patients with noninvasive bladder cancer treated with BCG. In both univariate and multivariate analyses of 343 high-risk bladder cancer patients undergoing BCG with a median follow-up of 116 months, hypertension was a statistically significant parameter prognostic for recurrence after BCG treatment. Further study is needed to both evaluate hypertension as a possible prognostic factor to be used in selecting poor-prognosis BC patients as early candidates for surgical treatment. [4]


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