BCG therapy, or Bacillus Calmette-Guérin therapy, is a type of immunotherapy used in the treatment of bladder cancer. It involves instilling the BCG vaccine directly into the bladder to stimulate an immune response against cancer cells. Here are key aspects of BCG therapy in treating bladder cancer:

1. **Immunostimulation:** BCG is a weakened form of Mycobacterium bovis, a bacterium related to the one that causes tuberculosis. When BCG is instilled into the bladder, it stimulates a local immune response. This immune response can target and destroy cancer cells in the bladder.

2. **Treatment for Superficial Bladder Cancer:** BCG therapy is commonly used for the treatment of superficial bladder cancer, which is cancer that has not invaded the muscle layer of the bladder. It is often used after transurethral resection of bladder tumor (TURBT), a surgical procedure to remove the tumor.

3. **Reducing Recurrence and Progression:** BCG therapy has been shown to be effective in reducing the recurrence of bladder cancer and preventing its progression to a more invasive form. It is often used as an adjuvant therapy after surgery to help prevent the cancer from coming back.

4. **Administration:** BCG is typically administered through a catheter into the bladder. The patient holds the BCG solution in the bladder for a certain period (usually about two hours) before voiding it out.

5. **Treatment Schedule:** BCG therapy is usually given in a series of treatments over several weeks. The exact schedule may vary depending on the specific treatment plan recommended by the healthcare provider.

6. **Side Effects:** BCG therapy can cause side effects, including urinary frequency, urgency, and discomfort during urination. Some patients may also experience flu-like symptoms, such as fever and fatigue. These side effects are generally temporary and resolve after the treatment is completed.

7. **Monitoring and Follow-up:** Patients undergoing BCG therapy are closely monitored for its effectiveness and for any signs of recurrence or progression of the disease. Regular follow-up examinations and cystoscopies are often part of the monitoring process.

It's important to note that while BCG therapy is effective for many patients, it may not be suitable for everyone. The decision to use BCG therapy is based on various factors, including the stage and grade of the bladder cancer, as well as the patient's overall health. The treatment plan is determined by a healthcare team specializing in the management of bladder cancer.