Targeted Drug Therapy for Thyroid Cancer

Newer drugs that specifically target the changes inside cells that cause them to become cancer are now being used to treat some thyroid cancers. These drugs are different from standard chemo drugs, and they often have different types of side effects.

The types of targeted drugs used to treat thyroid cancer are known as kinase inhibitors. Kinases are proteins inside cells that normally relay signals (such as telling the cell to grow). Blocking certain kinases can help treat some cancers.

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 when those treatments aren’t effective, targeted drugs can be helpful.

Multikinase inhibitors

Lenvatinib (Lenvima) and sorafenib (Nexavar) are targeted drugs known as multikinase inhibitors, because they can block several different kinase proteins. These drugs work in 2 main ways:

  • They help block tumors from forming new blood vessels, which the tumors need to grow.
  • They target some of the proteins made by cancer cells that normally help them grow.

These drugs can each help stop cancer growth for a time in people with differentiated thyroid cancer (papillary or follicular thyroid cancer) whose treatment with radioactive iodine is no longer working. It isn’t yet clear if these drugs help people live longer.

Both of these drugs are taken by mouth.

Common side effects can 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 more serious side effects can also occur. Ask your doctor what you can expect.

RET inhibitors

In some papillary and follicular thyroid cancers, the cells have certain changes in the RET gene that cause them to make an abnormal from of the RET kinase protein. This abnormal protein helps the cells grow. 

Selpercatinib (Retevmo) is a type of drug known as a RET inhibitor. It works by attacking the RET protein. This drug can be used to treat advanced papillary or follicular thyroid cancer if the cancer cells have certain types of RET gene changes, and radioactive iodine therapy is not a good option. 

This drug is taken by mouth as capsules, typically twice a day.

Common side effects of selpercatinib can include dry mouth, diarrhea, constipation, high blood pressure, feeling tired, swelling in the hands or feet, skin rash, high blood sugar levels, low white blood cell or blood platelet counts, and changes in certain other blood tests.

Less common but more serious side effects can include liver damage, allergic reactions, changes in heart rhythm, bleeding easily, and problems with wound healing.

NTRK inhibitors

A small number of thyroid cancers have changes in one of the NTRK genes. These gene changes can help cancer cells grow.

Larotrectinib (Vitrakvi) and entrectinib (Rozlytrek) target and disable the abnormal proteins made by the NTRK genes. These drugs can each be used in people with advanced thyroid cancer that has an NTRK gene change and is still growing despite other treatments.

These drugs are taken as pills, once or twice a day.

Common side effects of these drugs can include dizziness, fatigue, nausea, vomiting, constipation, weight gain, and diarrhea. Less common but more serious side effects can include liver damage, heart problems, and confusion and other nervous system problems.

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.

Multikinase inhibitors

Vandetanib (Caprelsa) and cabozantinib (Cometriq) are multikinase inhibitors (drugs that target several different kinase proteins). They can affect both cancer cells themselves and the growth of new blood vessels (which tumors need to grow).

These drugs can be used to treat advanced MTC. They each can stop cancers from growing for a time, although it is not yet clear if they can help people live longer.

These drugs are taken in pill form once a day.

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 or even life-threatening heart rhythm problems or infections. Because of its potential side effects, doctors must get special training before they are allowed to prescribe this drug.

Common side effects of cabozantinib 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.

RET inhibitors

In some medullary thyroid cancers, the cells have certain changes in the RET gene that cause them to make an abnormal from of the RET kinase protein. This abnormal protein helps the cells grow. 

Selpercatinib (Retevmo) is a type of drug known as a RET inhibitor. It works by attacking the RET protein. This drug can be used to treat advanced MTC if the cancer cells have certain types of RET gene changes. 

This drug is taken by mouth as capsules, typically twice a day.

Common side effects of selpercatinib can include dry mouth, diarrhea, constipation, high blood pressure, feeling tired, swelling in the hands or feet, skin rash, high blood sugar levels, low white blood cell or blood platelet counts, and changes in certain other blood tests.

Less common but more serious side effects can include liver damage, allergic reactions, changes in heart rhythm, bleeding easily, and problems with wound healing.

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.

BRAF and MEK inhibitors

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

Dabrafenib (Tafinlar) and trametinib (Mekinist) are drugs that target some of these proteins. (Dabrafenib affects the BRAF protein, while trametinib targets the related MEK protein.) 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.

RET inhibitors

In some anaplastic thyroid cancers, the cells have certain changes in the RET gene that cause them to make an abnormal from of the RET kinase protein. This abnormal protein helps the cells grow. 

Selpercatinib (Retevmo) is a type of drug known as a RET inhibitor. It works by attacking the RET protein. This drug can be used to treat advanced anaplastic thyroid cancer if the cancer cells have certain types of RET gene changes. 

This drug is taken by mouth as capsules, typically twice a day.

Common side effects of selpercatinib can include dry mouth, diarrhea, constipation, high blood pressure, feeling tired, swelling in the hands or feet, skin rash, high blood sugar levels, low white blood cell or blood platelet counts, and changes in certain other blood tests.

Less common but more serious side effects can include liver damage, allergic reactions, changes in heart rhythm, bleeding easily, and problems with wound healing.

NTRK inhibitors

A small number of anaplastic thyroid cancers have changes in one of the NTRK genes. These gene changes can help cancer cells grow.

Larotrectinib (Vitrakvi) and entrectinib (Rozlytrek) target and disable the abnormal proteins made by the NTRK genes. These drugs can each be used in people with anaplastic thyroid cancer that has an NTRK gene change and is still growing despite other treatments.

These drugs are taken as pills, once or twice a day.

Common side effects of these drugs can include dizziness, fatigue, nausea, vomiting, constipation, weight gain, and diarrhea. Less common but more serious side effects can include liver damage, heart problems, and confusion and other nervous system problems.

More information about targeted therapy

To learn more about how targeted drugs are used to treat cancer, see Targeted Cancer Therapy.

To learn about some of the side effects listed here and how to manage them, see Managing Cancer-related Side Effects.

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.

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Last Medical Review: March 14, 2019 Last Revised: May 12, 2020

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