Bacillus Calmette-Guérin (BCG) therapy is an immunotherapy that employs a weakened strain of Mycobacterium bovis, a bacterium related to the one causing tuberculosis. Developed by French scientists Albert Calmette and Camille Guérin in the early 20th century, this strain was named after them. First used in humans in 1921, BCG is now a widely utilized medical treatment.
How BCG Therapy Works
BCG therapy stimulates the body’s immune system to target and eliminate unwanted cells. When introduced, the weakened Mycobacterium bovis triggers a localized inflammatory response. This response attracts various immune cells, such as T-cells, macrophages, and natural killer cells, to the treatment site.
These immune cells recognize and become activated by the BCG bacteria. The activated immune cells then identify and attack abnormal cells, such as cancer cells, within the treated area. The therapeutic action relies on the immune system’s heightened activity, not direct destruction by BCG bacteria.
Its Primary Medical Application
BCG therapy is predominantly used to treat non-muscle invasive bladder cancer (NMIBC), which is cancer confined to the bladder lining and has not spread into the muscle wall. It is considered the main immunotherapy for early-stage bladder cancer.
This therapy helps prevent the cancer from recurring or progressing to more advanced stages. While it is also explored for other conditions, NMIBC remains its most common and established application.
Administering BCG Therapy
For bladder cancer, BCG therapy is administered through intravesical instillation. This involves inserting a thin tube, called a catheter, through the urethra and directly into the bladder. A liquid solution containing the BCG drug is then slowly infused into the bladder.
Patients retain the liquid in their bladder for up to two hours, allowing the BCG to interact with the bladder lining. After this period, the patient can urinate to expel the solution. Treatment typically begins with an induction phase of weekly treatments for six weeks, followed by maintenance treatments that can continue for up to three years, depending on recurrence risk.
Managing Side Effects
Patients undergoing BCG therapy may experience common side effects, which typically begin within a few hours and can last for one to three days. These include flu-like symptoms such as chills, muscle or joint pain, and a mild fever.
Urinary symptoms are also frequent, including an increased urge to urinate, more frequent urination, and a burning sensation or pain during urination. Some individuals might also notice a small amount of blood in their urine or feel fatigued. Patients should communicate any side effects to their healthcare providers for guidance on management.