The surprising way a TB vaccine harnesses your immune system to fight bladder cancer

While cancer treatment has advanced remarkably in recent years, a decades-old treatment that uses the body’s immune system to fight bladder cancer remains strong. BCG (Bacillus Calmette-Guérin) therapy, originally developed as a tuberculosis vaccine, continues to be an effective treatment for bladder cancer.

BCG is a form of immunotherapy treatment that stimulates the body’s own immune system to fight cancer cells in the bladder.

What is BCG?

BCG is a bacteria called Mycobacterium bovis and is very similar to the bacteria that causes tuberculosis. However, BCG has been altered so that it no longer causes infection in humans, but it still retains its ability to stimulate the immune system to help fight cancer.

When delivered directly to the bladder as a cancer treatment, BCG binds to both normal and cancerous cells in the bladder and causes an inflammatory environment. This allows your body’s immune system to recognize and destroy cancer. This form of cancer treatment is called immunotherapy.

Targeted immunotherapy that uses the body’s immune system to fight cancer has only been FDA-approved since 2012. However, BCG for bladder cancer is an earlier iteration of immunotherapy that’s been used since the 1980s.

How does BCG treat bladder cancer?

When you have a bacterial infection, your body’s immune system responds by arming itself to fight the threat. While cancer is not a bacterial infection, delivering BCG to the bladder is like sending a smoke signal to call in reinforcements. The immune system rushes to fight the invading bacteria, and in the process, the bladder cancer cells are caught in the crossfire and destroyed as unintended — albeit beneficial — collateral damage.

The bacteria isn’t a specific drug developed to fight cancer but is a brilliant way to stimulate the immune system to not only recognize itself but also to recognize and destroy the cancer cells.

This happens through the immune system’s two main components: the innate and adaptive immune systems. These systems work together to protect your body from infections and other harmful invaders like cancer cells.

Innate immune system: Your body’s first line of defense immediately responds to all threats, whether bacteria, viruses or cancer cells.

Adaptive immune system: This system is slower to respond initially, but it is highly specific and can “remember” pathogens and destroy them in the future.

Delivering BCG therapy directly to your bladder over time stimulates both parts of your immune system to destroy the cancer cells.

What to expect with BCG treatment for bladder cancer

BCG treatment for bladder cancer is administered through a catheter directly to the bladder. It takes only a short time to inject the drug into the bladder, and then the catheter is removed.

Your provider may ask you to gently roll side to side in order to coat the entire bladder. You can expect to be in the treatment room for about 30 minutes.

Ideally, you should hold the treatment in your bladder for two hours before urinating. If you do need to urinate before the two hour window is up, that’s OK.

The first treatment schedule for all patients is called induction therapy, which includes six doses of one treatment a week for six consecutive weeks.

Exposing the immune system to the bacteria weekly builds momentum or immune memory to fight abnormal cells.

The next stage after induction is called maintenance therapy, which consists of three-week cycles that occur every few months for up to three years.

Who is a candidate for BCG treatment?

Bladder cancer is classified into two different types based on how deeply the cancer cells have invaded the bladder wall.

1. Non-muscle-invasive bladder cancer (NMIBC)
2. Muscle-invasive bladder cancer (MIBC)

BCG is used primarily to treat NMIBC, which is limited to the bladder's inner lining and hasn’t yet invaded the deep muscle of the bladder.

MIBC has a greater risk of metastasizing, or spreading, making it more aggressive.

Within the category of NMIBC, there are three different subgroups based on the probability of the cancer recurring in the bladder or progressing to MIBC:

1. Low risk
2. Intermediate risk
3. High risk

Risk is determined by the likelihood the cancer will recur and progress once it’s initially treated.

Effectiveness of BCG in bladder cancer therapy

BCG treatment is highly effective in treating high-risk NMIBC. It’s also effective for intermediate-risk patients.

Cancer recurrence rates are significantly reduced with BCG. Receiving at least one year of BCG treatment reduces the chance the cancer will progress to MIBC.

Potential side effects of BCG treatment

Overall, BCG is a well-tolerated drug. However, some local side effects are common. This is because the therapy's goal is to stimulate an immune response, which causes your bladder to have a strong, inflammatory response.

Local side effects include the following:

• Frequent urination
• Urgency to urinate
• Burning while urinating
• Blood in urine

The problem often resolves within 24 hours of treatment.

Some people may also get a fever, feel fatigued and/or experience joint aches. These symptoms don't occur as commonly as the localized symptoms, often resolving with acetaminophen (Tylenol) or anti-inflammatory medications.

Still, many people aren’t able to work for a day or two immediately after treatment.

For people who experience more extended or increasingly uncomfortable side effects, your doctor can recommend strategies to help regulate your body’s inflammatory immune reaction. These include reducing the drug dosage, spreading out doses, or taking an antibiotic for a short period of time after treatment.

We know from large numbers of patients treated on clinical trials that most people can get through the three years of treatment successfully with careful symptom management by their providers.

In the 40 years since doctors started using BCG to treat bladder cancer, no other therapies have proved as effective as the tuberculosis vaccine.

Final tips for patients receiving BCG treatment for bladder cancer

• Avoid drinking a lot of liquids, especially coffee, before treatment so you can hold the medication in your bladder for two hours. However, don’t worry if you do need to urinate within two hours of treatment.
• After using the toilet the first time following treatment, add bleach and flush.
• Use a condom during intercourse for the entire course of therapy while either partner is being treated with BCG.
• Go to the hospital immediately if you experience a high fever after treatment. This rare side effect might be a sign the bacteria entered your bloodstream, which can cause sepsis.