Targeted therapy is a form of cancer treatment that uses drugs to specifically attack cancer cells while causing minimal harm to healthy cells. It is a cornerstone of precision medicine and works by focusing on the unique genetic changes and proteins that help cancer cells grow, divide, and spread.
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How Targeted Therapy Works
Unlike traditional chemotherapy, which kills all fast-dividing cells (including healthy ones), targeted therapy drugs are designed to interfere with specific "targets" that are crucial for a cancer cell's survival. These targets can be:
Proteins or enzymes on the surface of a cancer cell: These can be receptors that receive signals telling the cell to grow and divide.
Genetic changes or mutations inside the cell: These can be faulty genes that produce abnormal proteins that fuel cancer growth.
The tumor's microenvironment: This includes the blood vessels that supply the tumor with nutrients and oxygen.
By interfering with these targets, targeted therapy can:
Block or turn off growth signals: Preventing cancer cells from getting the messages they need to multiply uncontrollably.
Induce cell death (apoptosis): Causing the cancer cells to die in a controlled manner, a process they often evade.
Starve the tumor: Blocking the formation of new blood vessels (a process called angiogenesis) that a tumor needs to grow beyond a certain size.
Help the immune system find and destroy cancer cells: Marking cancer cells so the body's own immune system can more easily identify and attack them.
Deliver toxic substances directly to cancer cells: Some targeted therapies, called antibody-drug conjugates, act like a "Trojan horse" by carrying chemotherapy or a toxin directly to the cancer cell.
Types of Targeted Therapy Drugs
Most targeted therapy drugs fall into two main categories:
Small-molecule drugs: These drugs are small enough to easily enter cancer cells and target specific proteins inside them. They often block enzymes called kinases that are critical for cell growth. Examples include tyrosine kinase inhibitors (TKIs), which are used for a variety of cancers, including chronic myeloid leukemia and certain types of lung cancer.
Monoclonal antibodies: These are larger, lab-made proteins that are designed to attach to specific targets on the outside surface of cancer cells. They work in several ways, such as blocking growth signals or marking the cancer cells for destruction by the immune system. The names of monoclonal antibodies often end in "-mab." Examples include trastuzumab (Herceptin), which is used for HER2-positive breast cancer.
Who is a Candidate for Targeted Therapy?
Targeted therapy is not an option for everyone with cancer. To determine if a patient is a candidate, doctors perform specific genomic tests on the tumor tissue or blood. These tests look for genetic mutations or proteins that are known targets for a specific drug. Because targeted therapy is so precise, it will only work if the cancer cells have the specific "target" that the drug is designed to attack.
Side Effects
While targeted therapy is generally associated with fewer and less severe side effects than traditional chemotherapy, it can still cause side effects, which vary depending on the drug and the target. Common side effects can include skin rashes, diarrhea, and fatigue. The unique nature of targeted therapy can also lead to specific side effects, such as hand-foot syndrome from some drugs or high blood sugar levels.
Targeted therapy represents a major advancement in cancer treatment, allowing for a more personalized and effective approach to fighting the disease.
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