The human body has a sophisticated defense system against disease. Cancer, characterized by uncontrolled cell growth, challenges this system. Immunotherapy harnesses the body’s immune system to identify and eliminate cancer cells. This modern approach empowers natural defenses, unlike traditional direct cancer attacks. This article explores immunotherapy’s principles, applications in bladder cancer, and patient experiences.
Understanding Immunotherapy
The immune system constantly patrols the body, identifying and destroying abnormal cells, including cancerous ones. Immune cells, such as T cells, recognize cancer cells by specific markers, known as tumor antigens. Normally, these cells attack and clear diseased cells.
Cancer cells often evade immune surveillance by mimicking healthy cells, making them harder for the immune system to recognize. They may also produce proteins that interact with immune checkpoints, natural “brakes” that turn off the immune response. This allows cancer cells to proliferate and spread.
Immunotherapy aims to overcome evasion strategies by boosting or modifying the immune system’s ability to fight cancer. It works by “releasing the brakes” on immune cells or enhancing their capacity to identify and attack cancer cells. This enables the immune system to recognize, attack, and eliminate tumor cells, offering a targeted way to combat disease.
Types of Immunotherapy for Bladder Cancer
Immunotherapy for bladder cancer involves two main approaches: intravesical Bacillus Calmette-Guérin (BCG) and immune checkpoint inhibitors. Both stimulate an anti-tumor immune response.
Intravesical BCG is an immunotherapy for non-muscle invasive bladder cancer (NMIBC), confined to the bladder lining. It involves instilling a weakened tuberculosis bacterium directly into the bladder via a catheter. This triggers a localized immune response, attracting immune cells to the bladder lining, which destroy cancer cells. BCG stimulates an inflammatory reaction, helping prevent recurrence and progression.
Immune checkpoint inhibitors are another class of immunotherapy drugs. Medications like PD-1 or PD-L1 inhibitors block specific proteins on immune or cancer cells that act as “checkpoints.” These checkpoints normally prevent the immune system from overreacting, but cancer cells exploit them to hide from immune detection. Blocking these proteins, checkpoint inhibitors release the immune system’s natural brakes, allowing T cells to recognize and attack cancer cells, unleashing a robust anti-tumor immune response.
When Immunotherapy is Used in Bladder Cancer Treatment
Immunotherapy is used at various bladder cancer stages, depending on tumor invasiveness and spread. Its application is tailored to the disease’s characteristics, offering benefits for patient groups.
For non-muscle invasive bladder cancer (NMIBC), intravesical BCG is a standard treatment after tumor removal. It prevents recurrence or progression to a more invasive form. Treatment is given as a series of instillations directly into the bladder over several weeks, followed by maintenance therapy.
For muscle-invasive bladder cancer (MIBC), where cancer has grown into the deeper bladder wall, immunotherapy with checkpoint inhibitors may be used. It can be administered before surgery (neoadjuvant therapy) to shrink the tumor, or after surgery (adjuvant therapy) to reduce recurrence risk. For patients not candidates for surgery or with spread cancer, checkpoint inhibitors can be a primary treatment.
When bladder cancer has spread (metastatic bladder cancer), immune checkpoint inhibitors are often a primary treatment. They can be used as a frontline therapy or after other treatments. These systemic treatments control widespread disease and improve patient outcomes by engaging the immune system throughout the body.
What to Expect: Side Effects and Outcomes
Patients undergoing immunotherapy for bladder cancer may experience a range of side effects, differing from chemotherapy. Fatigue is common across immunotherapies. Patients might also experience flu-like symptoms, skin rashes, or diarrhea.
Specific side effects are linked to the type of immunotherapy received. For intravesical BCG, localized reactions within the bladder are common, including irritation, frequent urination, and blood in the urine. These symptoms are temporary and manageable.
Immune checkpoint inhibitors can lead to immune-related adverse events (irAEs), where the activated immune system mistakenly attacks healthy organs. These can affect various body systems, causing inflammation in the lungs, colon, liver, or endocrine glands. Patients should report new or worsening symptoms promptly, as early intervention can help manage these reactions.
Outcomes of immunotherapy for bladder cancer vary. While not every patient responds, some experience significant and durable responses, including long-term remission. Treatment aims to control cancer, improve quality of life, and in some instances, extend survival. Ongoing research refines treatment strategies and identifies factors predicting treatment success.