Targeted therapy for cancer

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on May 3, 2022.

Targeted therapy does its work by using drugs that are designed to seek out features unique to specific cancer cells or ones that influence their behavior. These characteristics may include enzymes, proteins or gene mutations that may be driving the cancer’s growth. Targeted therapy drugs are designed to either attack the cell directly or to help other cancer treatments, such as chemotherapy, work better. The drugs may also be used in combination with radiation therapy or surgery.

Targeted therapy is a form of chemotherapy (drug therapy) a type of precision cancer treatment. While traditional or standard chemotherapy targets fast-growing cells throughout the body, whether they’re cancerous or not, targeted therapy directs drugs to specific features of cancer cells. Traditional chemotherapy is designed to kill cancer cells the body has already made. Targeted therapies are designed to block or stop cancer cells from copying themselves and prevent new cancer cells from forming. Because they work differently, targeted therapies are less likely than traditional chemotherapies to kill normal cells.

Oncologists rely on advanced genomic testing and other laboratory tests or diagnostic procedures to determine whether an available targeted therapy may benefit a patient. The therapies are specific to the particular cancers they affect, or to specific features of cancer cells no matter where they appear in the body.

Targeted therapy drugs interfere with specific molecules found in receptors or proteins, on and in cancer cells. The goal with targeted therapy is to stop or slow tumor growth by interfering or attacking the genetic features of the cells that regulate growth and division. Unlike immunotherapy, which stimulates a person’s immune system to recognize cancer cells as foreign bodies and attack them, targeted therapy relies on the drugs it uses or carries to do the attacking.

How does targeted therapy work?

Cancer develops when the DNA in a cell mutates or becomes defective. Targeted therapy drugs are designed to bypass normal cells and zero in on specific targets—some are mutations on the surface of cancer cells, others are inside the cell. Once they reach their target, these drugs may:

  • Shut down signals that allow cancer cells to grow
  • Prevent cancer cells from making new blood vessels, which feed tumors
  • Stop production of hormones that may help tumors grow
  • Repair the ability of cells to shut down if they are defective
  • Carry radiation or chemotherapy drugs directly to the mutated cell

For example, trastuzumab (Herceptin®)—a drug designed to shut down cancer cell growth signals—is used in the treatment of some breast cancers. It targets defective human epidermal growth factor receptor 2 (HER2) proteins. HER2 is a protein found on the surface of normal cells that sends signals that help cells grow. But it runs amok in about 25 percent of breast cancer patients and ends up producing too many receptors, causing cancer cells to grow wildly.

Another example, Bevacizumab (Avastin®), is a drug that may disrupt a cancer’s ability to make new blood vessels, which would increase the blood supply it needs to feed itself.  All cells produce vascular endothelial growth factor (VEGF), a protein that helps cells form new blood vessels through a process called angiogenesis. Drugs such as bevacizumab, an angiogenesis inhibitor, are designed to block VEGF and stop a tumor from forming new food supplies.

How are the targets found?

Before determining whether to use a targeted cancer therapy, oncologists need to know where they are aiming. To assist in this form of precision medicine, certain tests may help determine which DNA mutation is driving the cancer’s behavior. These tests include:

Advanced genomic testing: In this analysis, the genetic profile of a tumor is scanned for specific mutations that may propel the tumor’s growth, progression or other behaviors. If a known mutation is found, it may be matched to a specific drug therapy targeting that mutation.

Pathology tests: These include examination of tissue samples, blood samples or stool samples. By searching for mutant proteins or an overabundance of protein in cancer cells, pathologists may identify potential targets for therapy. They may also look for abnormalities in chromosomes inside cancer cells.

Genetic testing: These tests may determine whether a patient has a hereditary gene mutation linked to his or her cancer.

What types of cancer drugs are used in targeted therapy?

There are different types of targeted therapy, depending on the specific cancer features detected. Below are some of the potential treatment options.

Monoclonal antibodies

Monoclonal antibodies, also known as therapeutic antibodies, are immune system proteins produced in a laboratory. These engineered molecules are designed to attach to specific targets found on cancer cells. They may directly stop cancer cell growth or cause the cancer cells to self-destruct. They may also be used to carry toxins such as chemotherapeutic agents or radioactive substances to tumor cells to cause cell death. In immunotherapy, monoclonal antibodies mark cancer cells so that they will be better seen and destroyed by the immune system.

Small-molecule drugs are better able to access cells and locate their prime target due to their low molecular weight and size. Some examples of small-molecule drugs include epidermal growth factor receptor (EGFR) inhibitors, angiogenesis inhibitors and apoptosis inducers.

EGFR inhibitors

Epidermal growth factor receptor (EGFR) is a protein, found on the surface of some normal cells, that contributes to cell growth. When cancer cells have a large number of these receptors, they’re able to grow and divide rapidly. EGFR inhibitors are used in targeted therapy to block these proteins and prevent cancer from growing.

Angiogenesis inhibitors

Angiogenesis inhibitors are another drug used in targeted therapy. Angiogenesis—the formation of new blood vessels—is controlled by chemical signaling. In healthy people, these chemical signals only appear when needed: during growth and healing. However, the signals may get crossed and allow blood vessels to grow abnormally. Tumors need a supply of blood to grow, and without it, they can’t grow or spread. The idea behind angiogenesis inhibitors is to prevent or block the supply of blood vessels that feed tumors in order to starve them to death. Angiogenesis inhibitors don’t block the growth of tumors, but rather the tumors’ blood supply. Angiogenesis inhibitors are typically given over a long period of time, in combination with other therapies.

Apoptosis inducers

To function normally, the body needs to shed unneeded and abnormal cells. It does so in a complex process of controlled cell death called apoptosis. Cancer cells are able to avoid apoptosis. Apoptosis inducers are used to allow apoptosis, helping to prevent recurrence and metastasis.

Hormone therapies

Hormone therapies target specific hormones, such as estrogen, to decrease the amount of that hormone in the body, slow the production of the hormones or block them entirely from feeding cancer cells.

What are side effects of targeted therapy?

Because the treatments are designed to target cancer cells and spare damage to healthy cells, targeted therapy drugs may cause fewer side effects than conventional treatments such as chemotherapy. However, depending on the type of targeted therapy used, the treatment may also alter cell function, potentially leading to side effects that should be monitored and managed.

Targeted therapy side effects may include:

Targeted therapy drugs are powerful and may cause side effects in caregivers and family members who come in contact with them. If you’re taking a targeted therapy at home, be aware of special handling, storage and disposal requirements.

What types of cancer do targeted therapies treat?

The U.S. Food and Drug Administration (FDA) has approved targeted therapy drugs for many cancers, including the most common types, such as:

The FDA has also approved targeted therapy drugs to treat solid tumors that have a neurotrophic receptor tyrosine kinase (NTRK) gene fusion. In these tumors, the NTRK gene has broken off one chromosome and fused with another, which may promote tumor growth. This is a tumor-agonistic therapy diagnosed based on specific genetic features of the cancer, regardless of where in the body it originated.

How are targeted therapy drugs delivered?

How and where targeted drugs may be given to cancer patients depend on many factors, including clinical considerations and personal preferences. They may be administered:

  • Orally: In pill, capsule or liquid form, taken by mouth, usually at home
  • By injection: Delivered through a needle into a vein, muscle or under the skin
  • By infusion: Delivered into a vein through an intravenous drip, a process that may take several hours

Small-molecule drugs are usually given in pill or capsule form. Monoclonal antibodies are usually given by injection or infusion. Patients whose treatment plan includes more frequent injections or infusions may choose a port or catheter to deliver their drug more efficiently and with less pain.

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