Targeted therapy
Targeted therapy is cancer treatment that uses drugs designed to act on specific molecules, proteins, pathways, or genetic changes that help cancer cells grow, survive, or spread. It is a major part of precision oncology, but it works only when the target matters and the tumor is vulnerable to the drug.
What targeted therapy is
Targeted therapy is cancer treatment built around particular features of cancer cells or their surroundings. Instead of broadly damaging fast-dividing cells, targeted drugs aim at molecules that help cancer grow, divide, repair itself, form blood vessels, avoid death, or communicate with nearby tissue. The target may be a protein, receptor, enzyme, signaling pathway, gene change, or cell-surface marker.
How it differs from chemotherapy
Chemotherapy often attacks processes common to rapidly dividing cells, which can affect both cancer cells and healthy cells. Targeted therapy is more selective in design, but selective does not mean harmless or always more effective. A targeted drug can still affect healthy tissues that use the same pathway, and a cancer can resist the drug if the target is absent, altered, or bypassed.
Biomarker testing
Many targeted therapies depend on biomarker testing. A tumor sample, blood test, or other laboratory method may look for mutations, gene fusions, protein expression, copy-number changes, or other features. Testing helps show whether a cancer has the target the drug is designed to affect. It can also help avoid treatment that is unlikely to work.
Small-molecule inhibitors
Small-molecule targeted drugs are usually able to enter cells and interfere with enzymes or signaling proteins inside them. Many are taken as pills or capsules. Examples include drugs that inhibit kinases, PARP, hormone-related pathways, or other molecular systems. Their names and targets vary widely because cancer growth can depend on many different pathways.
Monoclonal antibodies
Some targeted therapies are monoclonal antibodies. These larger molecules usually bind targets on the outside of cells or in the bloodstream. They may block a growth signal, mark cancer cells for immune attack, interfere with blood-vessel growth, or deliver a drug or radioactive particle to a target. Antibody-based therapies overlap with immunotherapy in some cases.
Precision oncology
Precision oncology tries to match treatment to the biology of a person's cancer rather than relying only on where the cancer started. This can mean matching a drug to a mutation, fusion, receptor, or pathway. It can also mean recognizing when a target exists but is not enough to predict benefit, because tumors are complex and can contain mixed cell populations.
Side effects
Targeted therapy side effects depend on the target and drug. They can include rash, diarrhea, high blood pressure, liver changes, bleeding or clotting problems, mouth sores, fatigue, heart effects, lung inflammation, wound-healing problems, low blood counts, or interactions with other medicines. Side effects may be different from chemotherapy, but they still need monitoring.
Resistance
Cancer can become resistant to targeted therapy. A tumor may develop a new mutation in the drug target, activate an alternate pathway, produce more of the target, change drug uptake or breakdown, or evolve into a mixed population where some cells survive. Resistance is one reason targeted therapies are often studied in combinations or sequences.
When it is used
Targeted therapy may be used alone, with chemotherapy, with immunotherapy, with hormone therapy, after surgery, for advanced cancer, or as maintenance treatment after an initial response. The exact role depends on the cancer type, stage, molecular findings, prior treatments, patient health, and treatment goals.
Why it matters
Targeted therapy matters because it changed cancer treatment from a mainly tissue-based approach toward a molecular one. It made some cancers more controllable, created new reasons to test tumors carefully, and helped show that cancers with the same name can behave differently. Its limits are just as important: targets must be meaningful, access to testing matters, and resistance can emerge.