Targeted therapies are medicines that affect a cancer cell's ability to grow and to spread. They focus on, or target, one or more changes found mainly on or in cancer cells, such as certain proteins or gene changes. This means they tend to have very different side effects than chemotherapy.

Tests can be done on your cancer cells to see if they have the changes that these medicines target. Many different medicines are used, and there are a lot of different targets these medicines act on.

Targeted therapy is mostly used to treat medullary thyroid cancers (MTCs) and anaplastic thyroid cancers. The usual iodine- and hormone-based treatments that work for other types of thyroid cancer often don't work for these cancers.

Papillary, follicular, and Hurthle thyroid cancers that don't respond to the usual treatments may be treated with targeted therapy, too.

Targeted therapy is usually managed by an oncologist. The targeted therapy given depends on your type of thyroid cancer. The targeted therapy medicines used for thyroid cancer are all taken as pills or capsules. You will take them at home once or twice a day. Targeted therapy medicines that may be used to treat thyroid cancer include:

• Sorafenib.
• Lenvatinib.
• Vandetanib.
• Cabozantinib.
• Selpercatinib.
• Pralsetinib.
• Larotrectinib.
• Entrectinib.
• Dabrafenib.
• Trametinib.
• Sunitinib.
• Axitinib.
• Everolimus.
• Pazopanib.

Even though the medicines are taken by mouth, they're still strong and can cause side effects.

Some of the more common side effects of targeted therapy are:

• Nausea.
• Dizziness.
• Diarrhea, which may be caused by an inflamed colon (colitis).
• Constipation.
• High blood pressure.
• Headache.
• Severe tiredness (fatigue).
• Decreased appetite.
• Weight loss or gain.
• Mouth sores.
• Skin problems, such as dryness, rash, blisters, or darkening skin.
• Problems with wound healing.
• Hand-foot syndrome (redness, pain, and swelling in hands or feet).
• Belly (abdomen) pain.
• Muscle and joint pain.
• Increased levels of blood sugar.
• Minor gastric bleeding.

Most of these side effects go away or get better over time after treatment ends. There may be things you can do to help control some of them.

These medicines can also cause severe side effects. They may include infection, changes in heart rhythm, lung inflammation, damage to the liver, or severe bleeding. But these are less common. Tell your doctors about any side effects you have. They can help you cope with the side effects.

Your doctor may test your kidney, thyroid, liver, and other functions during targeted therapy treatment.

It's important to know which medicines you're taking. Write down the names of your medicines. This includes prescription and over-the-counter medicines. Ask your care team how the medicines work. Find out what side effects they might cause. Tell them about any herbs, vitamins, and supplements you take. Some of these might interact with your targeted therapy.

Talk with your doctors about what symptoms to watch for and what to do if you have any. Ask them what changes you should call them about. For instance, some types of targeted therapy can cause rashes that might get worse if not treated right away. Know what number to call with any questions. Is there a different number for evenings, weekends, or holidays?

It may be helpful to keep a diary of your side effects. Write down any physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your care team to make a plan to manage your side effects.