Bacillus Calmette–Guérin (BCG) for superficial bladder cancer
Larry H. Bernstein, MD, FCAP, Curator
LPBI
Intravesical therapy for bladder cancer
http://www.cancercenter.com/bladder-cancer/intravesical-therapy/
Intravesical therapy is usually an option for people with noninvasive (stage 0) or minimally invasive (stage I) bladder cancer. With intravesical therapy for bladder cancer, drugs are put directly into the bladder through a catheter, instead of being injected into a vein or swallowed. Both immunotherapy and chemotherapy drugs can be given this way.
This approach is useful for earlier stage cancers because the drugs kill malignant cells on the bladder lining only. Intravesical therapy does not reach the deeper layers of the bladder wall, the kidneys, ureters or urethra. If cancer has spread to other organs, those tumors would also not be treated with intravesical therapy.
There are a few types of intravesical immunotherapy:
- Bacillus calmette-guerin (BCG) therapy: BCG is a type of intravesical immunotherapy, and can be an appropriate way to treat early-stage bladder cancer. BCG is a bacterium that does not cause any serious disease, but is related to the germ that causes tuberculosis. For bladder cancer treatment, BCG is inserted into the bladder through a catheter. The natural immune system becomes activated by the presence of the foreign bacteria, which then affects bladder cancer cells. BCG is usually given for one to six weeks, and may be given alongside transurethral resection. Less commonly, BCG is given as a long-term maintenance treatment.
- Interferon: Several types of cells in the body produce substances called interferons, which help stimulate the immune system. These natural chemicals can also be made artificially for use as medications to treat various diseases. One application of synthesized interferon is as an intravesical immunotherapy treatment for early-stage bladder cancer.
Intravesical Chemotherapy
As described above, with intravesical chemotherapy, anticancer drugs that directly kill active cancer cells are inserted directly into the bladder through a catheter. This approach helps avoid many harsh side effects that occur as a result of the drugs harming normal cells.
The drugs most commonly used in intravesical chemotherapy are mitomycin and thiotepa. Other drugs used in this approach include valrubicin, doxorubucin and gemcitabine. Sometimes, mitomycin is given as “electromotive mitomycin therapy,” which means that the bladder is heated while the drug is inserted.
Complications of intravesical BCG immunotherapy
INTRODUCTION
Intravesical administration of Bacillus Calmette-Guerin (BCG), a live attenuated strain of Mycobacterium bovis, has become a mainstay of adjunctive therapy for superficial bladder cancer. While generally well tolerated, both local and systemic infectious complications can arise. When disseminated BCG infection occurs, antituberculous therapy with or without glucocorticoids should be administered.
The infectious complications of BCG immunotherapy will be reviewed here. The clinical use of this agent for the treatment of superficial bladder cancer is discussed separately. Disseminated infection has also been rarely reported in patients receiving BCG vaccination for the prevention of tuberculosis [1]. (See “Treatment of non-muscle invasive bladder cancer” and “BCG vaccination”.)
PATHOGENESIS
The mechanism by which BCG leads to the development of infectious complications is not fully understood. Its mechanism of action as an immunotherapeutic agent in cancer is not fully known but recent evidence suggests that elaboration of a particular helper T cell cytokine profile known as the “Th1 response” is an integral part of its mechanism [2]. (See “Treatment of non-muscle invasive bladder cancer”, section on ‘Bacillus Calmette-Guerin’.)
Considerable debate exists in the literature about whether infectious complications due to BCG represent a hypersensitivity reaction or ongoing active infection. The hypersensitivity hypothesis gained early credence based upon the presence of granulomas and the absence of recoverable organisms. In a number of case reports, acid-fast bacilli have not been demonstrated and organisms have not grown despite a high clinical suspicion of BCG infection [3,4]. A response to glucocorticoids, administered along with antituberculous drugs, has also supported the notion of a hypersensitivity response.
In contrast, other case reports have demonstrated viable organisms in a variety of tissues, including lung [5], liver [6,7], pancreas [8], psoas abscess contents [9], mycotic aneurysm [10], bone marrow [11], vitreous fluid [12,13], and even the brain [14]. The fastidious growth nature of BCG in culture and a doubling time of 24 to 48 hours contribute to the difficulty in its isolation. M. bovis has also been demonstrated by PCR in some cases [15], although in other reports these studies have been negative [3]. Further compounding this story are several cases of delayed infection, months to even years after the original BCG administration [16,17].
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