Immunotherapy has revolutionized cancer treatment over the last few decades. Unlike traditional treatments like chemotherapy and radiation therapy, which directly target cancer cells, immunotherapy works by boosting the body’s natural defenses to identify and destroy cancer cells more effectively. The concept of harnessing the immune system to fight cancer was first proposed by William Coley, an American surgeon.
How Immunotherapy Works
The immune system plays a crucial role in protecting the body against infections and abnormalities, including cancer cells. However, cancer cells can evade detection by the immune system or suppress immune responses, allowing them to grow and spread unchecked. Immunotherapy aims to overcome these barriers by enhancing immune responses or targeting specific mechanisms that cancer cells exploit.
Types of Immunotherapy
Several types of immunotherapy have been developed, each with unique mechanisms and applications in cancer care:
- Checkpoint Inhibitors: Checkpoint inhibitors are drugs that target immune checkpoints, proteins that regulate immune responses. By blocking these checkpoints, drugs like pembrolizumab (Keytruda), nivolumab (Opdivo), and ipilimumab (Yervoy) help unleash the immune system to recognize and attack cancer cells more effectively. Checkpoint inhibitors are used in various cancers, including melanoma, lung cancer, bladder cancer, and certain types of advanced or metastatic cancers.
- CAR-T Cell Therapy: Chimeric Antigen Receptor T-cell therapy (CAR-T therapy) is a personalized treatment approach. T cells, a type of immune cell, are extracted from the patient’s blood and genetically engineered to express chimeric antigen receptors (CARs) on their surface. These modified CAR-T cells are then infused back into the patient, where they can recognize and destroy cancer cells expressing the targeted antigen. CAR-T cell therapy has shown remarkable success in treating certain blood cancers like acute lymphoblastic leukemia (ALL) and certain types of lymphomas.
- Monoclonal Antibodies: Monoclonal antibodies (mAbs) are laboratory-produced proteins that target specific molecules on cancer cells. They can work in various ways:
- Targeted Therapy: mAbs like trastuzumab (Herceptin) and pertuzumab (Perjeta) target HER2 receptors on breast cancer cells, blocking their growth signals.
- Immune System Activation: Antibodies such as rituximab (Rituxan) attach to CD20 proteins on B cells in lymphomas, marking them for destruction by the immune system.
- Immune Checkpoint Blockade: Antibodies like durvalumab (Imfinzi) and avelumab (Bavencio) target PD-L1, a protein that cancer cells use to evade immune attacks.
- Cytokine Therapy: Cytokines are signaling proteins that regulate immune responses. Interleukins (IL-2, IL-7, IL-12) and interferons (IFN-alpha, IFN-beta) are examples of cytokines used in cancer immunotherapy. They can stimulate immune cell activity against cancer cells, although their use is less common due to potential side effects.
- Oncolytic Virus Therapy: This innovative approach involves using genetically modified viruses that selectively infect and kill cancer cells while sparing healthy cells. Oncolytic viruses can also stimulate the immune system’s anti-tumor response, enhancing their therapeutic effects.
- Vaccines: Cancer vaccines aim to boost the immune system’s ability to recognize and attack cancer cells. Examples include the HPV vaccine for preventing cervical cancer and therapeutic cancer vaccines like Sipuleucel-T (Provenge) for prostate cancer.
Side effects of Immunotherapy
Immunotherapy, while offering promising results in cancer treatment, can also lead to various side effects known as immune-related adverse events (irAEs). These side effects occur due to the activation of the immune system and can affect different organs or systems in the body.
Common side effects of immunotherapy include fatigue, skin rash or itching, gastrointestinal issues like diarrhea, nausea, loss of appetite, and muscle or joint pain.
More severe irAEs can include inflammation of the lungs (pneumonitis), liver (hepatitis), or colon (colitis), severe skin reactions, and endocrine disorders affecting glands like the thyroid or pituitary.
Prompt recognition and management of these side effects are crucial to prevent complications.
Cost of Immunotherapy
The cost of immunotherapy can vary widely depending on several factors such as the type of cancer, specific immunotherapy drugs used, treatment duration, hospital or clinic charges, additional supportive medications, and any associated diagnostic tests or procedures.
Success Rates of Immunotherapy
The success rate of immunotherapy in cancer treatment varies widely depending on several factors, including cancer type, stage, specific immunotherapy drugs used, and individual patient characteristics.
Immunotherapy has shown remarkable efficacy in certain cancers, such as melanoma, lung cancer, kidney cancer, bladder cancer, and certain types of lymphomas. In some cases, immunotherapy can lead to durable responses and even long-term remissions, particularly in patients with tumors expressing specific biomarkers like PD-L1, high tumor mutational burden (TMB), or microsatellite instability (MSI).
Immunotherapy has led to durable responses and even long-term remissions in some patients with stage 4 cancer, but it may not be curative for everyone. Response rates vary among individuals, and not all patients will experience complete remission or long-lasting responses.
However, it’s important to note that not all patients respond to immunotherapy, and response rates can range from moderate to exceptional across different cancer types and individuals.
