Targeted therapy medicines attack specific proteins or cell functions that help cancer cells grow. Like chemotherapy, these medicines work throughout the body, but they work in different ways. This means they can sometimes be helpful even if chemotherapy isn’t working. These medicines mainly target cancer cells. So the side effects are often different and possibly less severe than those from chemotherapy medicines.

Not everyone with colorectal cancer will need targeted therapy. Deciding if you need targeted therapy will depend mainly on these factors:

• Whether you have colon or rectal cancer

• The stage of your cancer

• Traits of your cancer, such as specific proteins on the surface of the cancer cells

• Your age and general health

• Your concerns about side effects

• What treatments you may have had before

Targeted medicines are used to treat some colorectal cancers that have spread to other parts of the body. Some of these medicines are also being studied to see if they might help if given after surgery for less advanced cancers. 

These medicines are most often given along with chemotherapy. But some may also be used alone if chemotherapy is no longer working. 

Several targeted medicines are now used for colorectal cancer.

Tumors need new blood vessels to grow beyond a certain size. Some targeted medicines work by blocking new blood vessels from forming. These include:

• Bevacizumab

• Ramucirumab

• Ziv-aflibercept

EGFR is a protein that is often found in high levels on cancer cells and helps them grow. Some targeted medicines work by attacking the EGFR protein. These include:

• Cetuximab

• Panitumumab

These medicines don’t work in people whose cancer cells have certain gene mutations. Your healthcare provider will test a sample of your tumor for these mutations before you get one of these medicines.

Regorafenib is a type of targeted medicine known as a kinase inhibitor. It can affect several different proteins (kinases) in cancer cells that normally help them grow.

Before treatment starts, you will meet with a medical oncologist. This is a healthcare provider who specializes in treating cancer with medicines. He or she will discuss your treatment options with you and explain what you might expect. 

Depending on the medicines you are taking, they may be pills that you swallow. Or you may get them through an IV (intravenous) line in a vein. This may take several minutes or hours.

In most cases, you will have targeted therapy as an outpatient. That means that you get it at a hospital, clinic, or healthcare provider's office, and you go home the same day. In some cases, you may need to stay in the hospital during treatment.

You'll be watched for reactions during your treatments.

Some targeted medicines are given along with chemotherapy. Others are given alone.  

Side effects of targeted therapy are somewhat different for everyone. They also vary based on which type of medicine you get. Ask your healthcare provider for more details about possible side effects. Tell your provider about any changes or side effects you notice. They can suggest things to make you feel better. In most cases, you’ll stop having side effects a few weeks after your treatment ends. Below is a list of some of the possible side effects, grouped by the type of targeted medicine.

Possible side effects from medicines that target new blood vessel growth include:

• Allergic reactions. If you have a reaction, it will likely be short-term and treatable. Your healthcare provider will decide if you can keep taking this type of medicine.

• High blood pressure

• Increased chance of blood clotting with an increased risk for heart attack and stroke. Your healthcare provider will watch you for this side effect. Report right away if you have chest pain, shortness of breath, or numbness or weakness, or if you feel dizzy or faint. 

• Increased chance of an opening in the stomach or intestine called GI perforation. Report right away any new pain, constipation, or vomiting.

• Increased chance of healing delay in surgical wounds. Let your healthcare provider know if you have any wounds that aren’t healing well.

• Increased chance of bleeding inside the body. Symptoms include coughing up blood, having blood in your stools or urine, or bleeding from your nose or gums.

• Increased chance for infection because of a low white blood cell count

• Feeling very tired. This occurs during and for a while after treatment.

• Spilling of protein in the urine, a sign of kidney damage. Your healthcare provider will check a urine sample before and during your treatment to see if there is too much protein in it.

Possible side effects from medicines that target the EGFR protein include:

• Acne-like skin changes on your face and chest. Treatment can’t prevent these skin changes. But there are some ways to make them less of a problem.

• Allergic reactions. If you have a reaction, it will likely be short-term and treatable. Your healthcare provider will decide if you can continue to get this type of medicine.

• Diarrhea

• Fever

• Headache

• Feeling very tired. This occurs during and for a while after treatment.

Possible side effects from regorafenib include:  

• Diarrhea

• Hand-foot syndrome. Symptoms include redness, irritation, or pain in your hands and feet.

• High blood pressure

• Infection

• Increased chance of an opening in the stomach or intestine called GI perforation. Symptoms include pain, constipation, or vomiting.

• Increased chance of bleeding inside the body. Symptoms include coughing up blood, blood in your stools or urine, or bleeding from your nose or gums.

• Feeling very tired. This occurs during and for a while after treatment.

• Liver damage. Symptoms include yellowing of your skin or the whites of your eyes.

• Loss of appetite and weight loss

• Belly (abdominal) pain

• Sores in the mouth and throat

It's important to know which medicines you're taking. Write your medicines down. Ask your healthcare team how they work and what side effects they might have.

Talk with your healthcare providers about what signs to look for and when to call them. Know what number to call with questions. Is there a different number for evenings and weekends?

It may be helpful to keep a diary of your side effects. 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 healthcare team to make a plan to manage your side effects.