What Is Targeted Therapy?

Targeted therapy uses drugs or other substances to attack specific features found in or on cancer cells. These features may be gene mutations, abnormal proteins, or growth signals that the cancer depends on. Instead of broadly killing rapidly dividing cells, targeted therapy tries to interfere with a particular weakness in the tumor.

A simple way to think about it is this: if a cancer cell depends on a certain signal to keep growing, targeted therapy aims to block that signal. In some cases, it shuts down a growth pathway. In others, it blocks blood vessel formation, helps trigger cancer cell death, or carries treatment directly to cancer cells.

How Does Targeted Therapy Actually Work?

Targeted therapy works by interfering with the biological processes cancer cells rely on. According to the National Cancer Institute, targeted therapies can block or turn off chemical signals that tell cancer cells to grow, prevent tumors from making new blood vessels, cause cancer cell death, deliver toxic substances directly to cancer cells, or help the immune system destroy cancer cells.

The exact mechanism depends on the drug and the target involved. Some targeted therapies work outside the cell by attaching to a marker on the cell surface. Others work inside the cell by blocking internal pathways that control survival and division. The American Cancer Society groups targeted therapies broadly into small-molecule drugs and monoclonal antibodies. Small-molecule drugs are small enough to enter cells and act on targets inside them, while monoclonal antibodies usually work on targets found on the outside of cells.

Why Is Targeted Therapy Different from Chemotherapy?

The biggest difference is specificity. Chemotherapy generally attacks cells that divide quickly, which includes cancer cells but also some healthy cells such as those in the hair follicles, digestive tract, and bone marrow. Targeted therapy is designed to act more selectively on cancer-related changes. The American Cancer Society notes that targeted therapy is meant to stop cancer cells from growing and spreading while limiting damage to normal, healthy cells.

That does not mean targeted therapy has no side effects or that it is automatically better than chemotherapy in every situation. It means the treatment is chosen because there is something specific about the tumor that the drug is designed to target.

Who Can Receive Targeted Therapy?

Not every patient is a candidate for targeted therapy. These treatments are usually most useful when a tumor has a biomarker, mutation, or other molecular feature that the drug is designed to target. That is why doctors often recommend biomarker testing, also called tumor testing, tumor profiling, or tumor genetic testing, before treatment. NCI explains that biomarker testing finds changes in a cancer that could help doctors choose treatment.

This is a key part of precision medicine. Two people may both have lung cancer, breast cancer, or colorectal cancer, but only one may have a targetable change that makes targeted therapy a good option. In that sense, the question is not only what type of cancer a person has, but also what is driving that cancer at the molecular level.

Where Does Liquid Biopsy Fit In?

In some situations, doctors may use a liquid biopsy to help guide targeted therapy. NCI has reported that FDA-approved liquid biopsy tests can identify genetic changes in tumor DNA shed into the blood and help doctors choose a targeted therapy or immunotherapy that is more likely to work. Tumor markers that indicate whether someone is a candidate for a targeted therapy can sometimes be measured from tumor tissue or from tumor material found in blood.

This does not mean liquid biopsy replaces every tissue biopsy. It means blood-based testing can sometimes add useful information, especially when tissue is limited or when doctors want to track how a cancer is changing over time.