Targeted Cancer Therapy

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Side effects of targeted cancer therapy drugs

What causes side effects?

Although targeted therapy drugs don’t affect the body the same way that standard chemo drugs do, they can still cause side effects. There are many different types of targeted drugs, and the side effects from these drugs depend largely on what each drug targets. Some drugs target substances that are more common on cancer cells, but are also found on healthy cells. These drugs can affect healthy cells, too, causing side effects.

Some types of targeted drugs seem to cause more side effects than others. For example, when drugs attack more than one target, side effects are more likely. Drugs that act as angiogenesis inhibitors affect new blood vessel growth all over the body, not just near the cancer, which can lead to side effects. Some drugs that boost the immune system can sometimes cause it to attack other parts of the body, which can also lead to side effects.

What should I know about side effects?

  • Not every person gets every side effect, and some people get few, if any.
  • The severity of side effects can vary greatly from drug to drug and from person to person. Be sure to talk to your doctor and nurse about which side effects are most likely with your treatment, how long they might last, how bad they might be, and when you should call the doctor’s office about them.Your doctor may give you medicines to prevent some side effects before they happen or to treat certain side effects once they occur.
  • Rare and unusual side effects can happen with some of these drugs, and some can be serious. All changes and side effects should be reported to your doctor.
  • Although side effects can be unpleasant, the less serious ones must be measured against the need to fight the cancer.

How long do side effects last?

Most side effects go away over time after treatment ends and the healthy cells recover. The time it takes to get over some side effects and regain energy varies from person to person. It depends on many factors, including your overall health and the drugs you were given.

Because many targeted drugs are still quite new, it’s hard to say how long you can expect side effects to last. We do know that some of the side effects from standard chemo drugs can last a lifetime, such as when the drug causes long-term damage to the heart, lungs, kidneys, or reproductive organs. In many cases we still don’t know if targeted therapy drugs cause these kinds of long-term changes.

Patients often become discouraged about how long their treatment lasts or the side effects they have. If you feel this way, talk to your doctor. You may be able to change your medicine or treatment schedule. Your doctor or nurse may be able to suggest ways to reduce problems or discomfort.

What are some of the more common and serious side effects of targeted drugs?

Before cancer treatment starts, most people worry about whether they will have side effects and, if so, what they will be like. Here’s a review of some of the more common and serious side effects caused by targeted therapy drugs. This is not a complete list, as each targeted drug can have different side effects.

Again, it’s important to know that not all targeted drugs cause all of these side effects. Talk to your doctor or nurse about which ones are most likely with the treatment you’re getting.

Skin problems

Some targeted drugs, especially those in the group called EGFR inhibitors, can cause rashes or other skin changes. These problems usually develop slowly over days to weeks. Skin changes (and ways to help manage them) are discussed in detail in the next section.

High blood pressure

Some targeted drugs, especially those called angiogenesis inhibitors, can raise your blood pressure. There isn’t really anything you can do to prevent this, but your doctor will watch your blood pressure closely if you are getting a drug that can cause this side effect. Some people need medicine to bring their blood pressure down to safe levels during treatment. They should stay on this medicine until their doctor tells them it can be stopped.

Problems with bleeding or blood clotting

Angiogenesis inhibitors interfere with new blood vessel growth. This can lead to problems with bruising and bleeding. Bleeding, such as from the stomach and intestines, can be severe and even life threatening. Tell your doctor if you throw up blood or material that looks like coffee grounds, or if you notice dark or black stools or bright red blood in your stool. These can be signs of bleeding in the stomach or intestines.

These drugs can also cause blood clots in the lungs and legs, as well as heart attacks and strokes. Let your doctor know if you have problems with sudden swelling, pain, or tenderness in the arm or leg. If you have chest pain, sudden shortness of breath, vision problems, weakness, seizures, or trouble speaking, get emergency help. These can be symptoms of serious problems caused by blood clots.

These problems are not common, and there is no way to prevent them. If something like this happens, you may need to stop taking the targeted drug.

Problems with wound healing

By blocking new blood vessel growth, angiogenesis inhibitors also interfere with wound healing. This can lead to old wounds (cuts) opening up again and new wounds not closing. It can also lead to holes opening up in the stomach or intestine (called perforations). Tell your doctor right away if you have pain in your belly or vomiting.

Because these drugs can affect wound healing, they usually need to be stopped before any planned surgery, including dental procedures. Talk to your cancer doctor as soon as you know about a planned surgery or other procedure so you can find out what to do.

Heart damage

Drugs called HER2 inhibitors can damage the heart, especially if used with certain chemotherapy drugs. Your doctor will probably get tests of your heart function before treatment. Possible symptoms of heart damage might include chest pain, increased coughing, trouble breathing (especially at night), rapid weight gain, dizziness, fainting, or swelling in the ankles or legs. Tell your doctor right away if you start to notice any of these symptoms once treatment starts.

Autoimmune reactions

Drugs called immune checkpoint inhibitors work by basically taking the brakes off the body’s immune system. This can lead to serious side effects if the immune system starts to attack other parts of the body. In some people this can cause serious reactions in the lungs, intestines, liver, skin, eyes, nerves, hormone-making glands, or other organs. This is not common but in some people it might be serious enough to be life threatening.

If you are getting one of these drugs, it’s very important to tell your doctor or nurse right away about any new side effects you are having. Treatment may need to be stopped. Sometimes people need to take drugs to suppress their immune systems.

Other side effects

Other side effects have also been linked to treatment with some targeted therapy drugs. Many of these side effects are the same as those that can be seen with standard chemotherapy drugs (although they are sometimes less severe). These include:

  • Nausea and vomiting
  • Diarrhea or constipation
  • Mouth sores
  • Shortness of breath or trouble breathing
  • Cough
  • Feeling tired all the time (fatigue)
  • Headache
  • Swelling in the hands and feet
  • Damage to organs such as the thyroid gland, liver, or kidneys
  • Allergic reactions (while getting an IV drug)
  • Increased risks of certain infections
  • Second cancers

You can learn more about some of these side effects and how to manage them in our booklet A Guide to Chemotherapy.

Keep in mind that these are not all of the side effects that people have, just some of the more common ones. Each drug can have different effects. To find out more about a drug you are taking, call us at 1-800-227-2345.

Your health care team will watch you closely during treatment and will check you often. Side effects can and should be treated as early as possible. It’s important that you tell your health care team about any changes in how you feel or anything you notice that’s new or unusual. Tell them right away so they can treat any problems and try to keep them from getting worse.


Last Medical Review: 12/08/2014
Last Revised: 12/11/2014