Many people wonder if immunotherapy and chemotherapy are the same, given that both are cancer treatments. While both therapies aim to control or eliminate cancer, they employ fundamentally different approaches to achieve this goal. This article explains the unique mechanisms, applications, and characteristics of chemotherapy and immunotherapy.
Understanding Chemotherapy
Chemotherapy is a systemic cancer treatment that uses drugs to destroy cancer cells or slow their growth. Its mechanism targets rapidly dividing cells. Cancer cells typically divide faster than most healthy cells, making them a target for these medications.
However, chemotherapy agents cannot differentiate between rapidly dividing cancer cells and healthy, fast-growing cells, such as those in hair follicles, the lining of the digestive tract, and bone marrow. This non-specific targeting explains common side effects of chemotherapy, including hair loss, nausea, vomiting, fatigue, and myelosuppression. It is administered in various ways, including intravenous infusions, oral pills, or injections.
Understanding Immunotherapy
Immunotherapy represents a different approach to cancer treatment, focusing on harnessing the immune system to fight cancer. Instead of directly attacking cancer cells, it stimulates or enhances the immune system’s ability to recognize and destroy abnormal cells. Cancer cells often evade detection by sending signals that trick immune cells.
Immunotherapy drugs can counteract these evasion strategies, unlocking the immune system’s ability to identify and target cancer. Different forms exist, including checkpoint inhibitors, which block proteins that prevent immune cells from attacking cancer, and CAR T-cell therapy, which modifies T-cells to target cancer cells. Side effects are often related to an overactive immune system, causing inflammation in various organs, resembling autoimmune reactions.
Fundamental Differences
The core distinction between chemotherapy and immunotherapy lies in their targets and mechanisms. Chemotherapy directly attacks and damages rapidly dividing cells, aiming for broad destruction of cancer. This direct approach means effects are often immediate, leading to rapid tumor shrinkage.
Conversely, immunotherapy does not directly target cancer cells; instead, it empowers the immune system to identify and eliminate them. This indirect mechanism means effects can take longer to manifest as the immune response builds. While chemotherapy is less specific, affecting healthy, fast-growing cells, immunotherapy aims to be more specific by enabling the immune system to distinguish cancer from healthy cells.
The differing mechanisms lead to distinct side effect profiles. Chemotherapy’s side effects arise from its non-specific targeting of rapidly dividing cells, while immunotherapy’s side effects often stem from an overstimulated immune system. Additionally, chemotherapy’s effects typically cease once drugs are no longer in the body, whereas immunotherapy can provide long-lasting protection as the immune system develops a “memory” of cancer cells.
Combining Therapies
Despite their different approaches, chemotherapy and immunotherapy are frequently used together as part of a cancer treatment strategy. This multimodal approach leverages the strengths of each therapy for better outcomes. For instance, chemotherapy can rapidly reduce tumor size, making cancer cells more vulnerable or “visible” to the immune system.
Combining therapies can also lead to a more sustained and durable response against cancer. The rationale for combination therapy is complex, depending on the cancer type, stage, and patient’s overall health. Treatment decisions are individualized, with oncologists considering the benefits and risks of each approach, whether alone or in combination.