Bacillus Calmette Guérin

Definition

BCG, or bacillus Calmette Guérin, is a genetically engineered bacterium that is used to treat bladder cancer . BCG is also known by the brand names ImmuCys, TheraCys and TICE BCG.

Purpose

Excision (cutting out) of bladder tumors can lead to extreme discomfort in patients because of the damage done to the bladder, the organ that collects and holds urine until it can be released from the body. In certain kinds of bladder cancers, treatment with BCG seems to cause cancers to shrink or disappear. Thus, when BCG treatment is effective, it is possible to preserve the bladder.

Description

BCG is made by altering the DNA, or hereditary material, of a bacterium. The bacterium that is altered is one that has been used for decades to vaccinate against tuberculosis. There are several different ways in which BCG has been modified by genetic engineering. In each case, however, the DNA added to the BCG from human cells gives instructions for the production of compounds that stimulate the immune system. The compounds are all proteins and are known by the scientific category name of cytokines.

Even BCG that has not been modified by genetic engineering seems to reduce the growth of superficial tumors in the bladder. But when the BCG introduced to the bladder contains DNA that gives instructions for cytokines, the tumor-fighting ability it confers on the organ is greater.

The live BCG is put inside the bladder where it causes an inflammatory response. This means that the bladder responds as though an infection were present and mounts an attack from the body's immune system. Somehow the response inhibits, or stops, tumor growth, but the way it does so is not understood.

Recommended dosage

BCG is delivered directly to the bladder via a catheter, or a tube that is inserted in the urethra. The method of delivery is called intravesical, which means it is sent directly into the cavity, or holding space, of the bladder.

The patient takes treatment once a week for six weeks and then once a month for six to twelve months. Large quantities of BCG are used. One standard dose of TheraCys calls for 81 milligrams in the first series of treatments.

Precautions

Care providers who have an immune system that is not functioning optimally should not handle BCG. Patients with HIV are at high risk for infection from BCG. All materials from BCG administration are considered biohazards.

Side effects

Most side effects fall into the category of flu-like symptoms and include chills, fever , and nausea and vomiting . There is also discomfort related to the inflammation of the bladder, particularly the feeling of an urgent need to urinate.

In a very few individuals BCG has spread throughout the body and caused infection and death.

Interactions

Antibiotics , or drugs given to fight infection, can stop the activity of the BCG and should not be given at the same time. Chemicals that suppress the immune system can also interfere with the action of BCG, as can radiation therapy .

Diane M. Calabrese

KEY TERMS

Catheter

—An artificial tube that is inserted in the urethra to introduce substances to the bladder, or under some circumstances, to drain the bladder.

Genetically engineered

—An organism that has been modified by the intervention of humans, usually by the addition of DNA, or hereditary material, from one species to the DNA of another species.

Kilogram

—Metric measure that equals 2.2 pounds.

Milligram

—One-thousandth of a gram. There are one thousand grams in a kilogram. A gram is the metric measure that equals about 0.035 ounces.

Urethra

—Tube that connects the bladder to the outside of the body.