Targeted Therapy for Thyroid Cancer

Researchers have begun to develop newer drugs that specifically target the changes inside cells that cause them to become cancerous. Unlike standard chemotherapy drugs, which work by attacking rapidly growing cells in general (including cancer cells), these drugs attack one or more specific targets on cancer cells.

Targeted drugs for medullary thyroid cancer

Doctors have been especially interested in finding targeted drugs to treat medullary thyroid cancer (MTC) because thyroid hormone-based treatments (including radioactive iodine therapy) are not effective against these cancers.

Vandetanib (Caprelsa) is a targeted drug taken as a pill once a day. In patients with advanced MTC, vandetanib stops cancers from growing for an average of about 6 months, although it is not yet clear if it can help people live longer.

Some common side effects of vandetanib include diarrhea, rash, nausea, high blood pressure, headache, fatigue, decreased appetite, and belly (abdominal) pain. Rarely, it can also cause serious problems with heart rhythm and infection that can lead to death. Because of its potential side effects, doctors must get special training before they are allowed to prescribe this drug.

Cabozantinib (Cometriq) is another targeted drug used to treat MTC. It is taken in pill form once a day. In MTC patients, cabozantinib has been shown to help stop cancers from growing for about 7 months longer than a sugar pill. So far, though, it has not been shown to help patients live longer.

Common side effects include diarrhea, constipation, belly pain, mouth sores, decreased appetite, nausea, weight loss, fatigue, high blood pressure, loss of hair color, and hand-foot syndrome (redness, pain, and swelling of the hands and feet). Rarely, this drug can also cause serious side effects, such as severe bleeding and holes in the intestine.

Targeted drugs for papillary or follicular thyroid cancer

Fortunately, most of these cancers can be treated effectively with surgery and radioactive iodine therapy, so there is less need for other drugs to treat them. But for cancers in which these treatments aren’t effective, targeted drugs can be helpful.

Sorafenib (Nexavar) and lenvatinib (Lenvima) are targeted drugs known as kinase inhibitors. They work in 2 ways. They help block tumors from forming new blood vessels, which the tumors need to grow. These drugs also target some of the proteins made by cancer cells that normally help them grow.

These drugs can help stop cancer growth for a time when given to patients with differentiated thyroid cancer (papillary, follicular, and poorly differentiated thyroid cancers) whose cancers no longer respond to treatment with radioactive iodine. It isn’t yet clear if these drugs help patients live longer.

Both of these drugs are taken by mouth.

Common side effects include fatigue, rash, loss of appetite, diarrhea, nausea, high blood pressure, and hand foot syndrome (redness, pain, swelling, or blisters on the palms of the hands or soles of the feet). Other side effects can also occur, some of which can be serious. Ask your doctor what you can expect.

Targeted drugs for anaplastic thyroid cancer

Doctors have been very interested in finding targeted drugs to treat anaplastic thyroid cancer because most other treatments are not very effective against these cancers.

Some anaplastic thyroid cancers have changes in the BRAF gene, which causes them to make proteins that help them grow.

Dabrafenib (Tafinlar) and trametinib (Mekinist) are drugs that target some of these proteins. These drugs can be used together to treat anaplastic thyroid cancers that have a certain type of BRAF gene change and that can’t be removed completely with surgery. 

These drugs are taken as pills or capsules each day.

Common side effects can include skin changes, rash, itching, sensitivity to the sun, headache, fever, chills, joint or muscle pain, fatigue, cough, hair loss, nausea, diarrhea, and high blood pressure.

Less common but serious side effects can include bleeding, heart rhythm problems, liver or kidney problems, lung problems, severe allergic reactions, severe skin or eye problems, and increased blood sugar levels.

Some people treated with these drugs develop skin cancers, especially squamous cell skin cancers. Your doctor will want to check your skin often during treatment. You should also let your doctor know right away if you notice any new growths or abnormal areas on your skin.

For general information about targeted therapy, see Targeted Therapy.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: March 31, 2016 Last Revised: May 4, 2018

American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.