Colorectal cancer

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Side effects of targeted therapy for colorectal cancer

Side effects can happen with any type of treatment for colorectal cancer, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

Chemotherapy and radiation therapy can cause side effects because they damage healthy cells as they kill cancer cells. Because targeted therapy doesn’t usually damage healthy cells, it tends to cause fewer and less severe side effects than these treatments. If side effects develop, they can happen any time during, immediately after or a few days or weeks after targeted therapy. Sometimes late side effects develop months or years after targeted therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of targeted therapy will depend mainly on:

  • the type of drug or drug combination given
  • the dose
  • how the drug is given (intravenously or orally)
  • your overall health

Tell your healthcare team if you have these side effects or others you think might be from targeted therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Flu-like symptoms

Flu-like symptoms are a common side effect of many targeted therapies. These symptoms include:

  • fever
  • chills
  • headache
  • muscle and joint pain
  • nausea and vomiting
  • loss of appetite

Flu-like symptoms develop most often after the first treatment and usually occur immediately. Flu-like symptoms usually lessen with time and go away with continued therapy when the body gets used to the drug.

Check with your doctor or healthcare team if these symptoms do not go away or are bothersome. They may suggest medicines, such as acetaminophen (Tylenol, Atasol), to help reduce some of these symptoms.

Find out more about flu-like symptoms like nausea and vomiting and loss of appetite.

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Fatigue is a common, but temporary, problem that can occur with many targeted therapy drugs. Fatigue makes you feel more tired than usual and can interfere with daily activities and sleep. It is often related to the dose of drug given and usually goes along with flu-like symptoms. Cetuximab (Erbitux) can lower levels of magnesium in the blood, which causes fatigue.

Tell your healthcare team if you are bothered by fatigue.

Find out more about fatigue.

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Skin problems

Targeted therapy drugs can cause skin problems during therapy and for some time afterward. The skin can become red, itchy and dry. It may start to peel. Some people develop a rash and acne on the face and body. Skin around the nails can become swollen and red. Skin can crack, or painful sores can open. Most targeted therapy drugs for colorectal cancer are given by injection, and the area around the injection site may become swollen or red. A rash can appear shortly after the injection.

Cetuximab (Erbitux) and panitumumab (Vectibix) commonly cause skin problems. Regorafenib (Stivarga) can cause hand-foot syndrome, which is a group of symptoms that include pain, tingling, numbness, redness and scaling or shedding of skin on the hands, feet or both.

Your healthcare team can suggest lotions, creams or other medicines to help relieve skin problems. Sun exposure can make skin problems worse, so you should protect your skin from the sun while you are receiving targeted therapy. When you go outside, use sunscreen and wear a hat, long-sleeved shirt and pants.

Find out more about skin problems.

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Sore mouth and throat

Many targeted therapy drugs can cause a sore mouth (also called stomatitis or oral mucositis). It occurs more often when higher doses of drugs are used. Painful sores, ulcers or infection can develop in the mouth, throat or gums. A sore mouth and throat can develop within 2 weeks of starting the therapy. These side effects quickly improve after treatment is finished.

Thorough, regular mouth care can help reduce infection and prevent a sore mouth and throat. The healthcare team will tell you how often to clean and rinse your mouth and what to use. They may prescribe pain medicines or special oral solutions to relieve pain.

Find out more about sore mouth and throat and mouth care.

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Pain is a common side effect of most targeted therapy drugs. Muscle, joint and abdominal pain usually happens at the same time as other flu-like symptoms. Abdominal pain may also happen with bowel problems. Bone pain develops because targeted therapy drugs increase the production of blood cells in the bone marrow. The extra blood cells cause pressure in the middle of the bone.

Pain usually goes away after the body adjusts to the targeted therapy drug. Your healthcare team may prescribe medicines to help relieve pain.

Find out more about pain.

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Bowel problems

Bowel problems may happen with targeted therapy for colorectal cancer. These problems usually go away after treatment is finished, but some problems can last several months or years after targeted therapy.

Diarrhea or constipation may occur during targeted therapy for colorectal cancer. Diarrhea is an increase in the number and looseness of stools. Constipation is when stools become hard, dry and difficult to pass. Find out more about diarrhea and constipation.

Bowel perforation is a hole or tear in the intestine. It is a rare but serious side effect of some types of targeted therapy.

The healthcare team can suggest ways to help manage bowel problems. They may prescribe medicines for diarrhea or constipation. Surgery is usually needed to fix a bowel perforation.


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Bone marrow suppression

Bone marrow suppression is a condition in which one or more of the main types of blood cells are decreased.

  • A low white blood cell count is called neutropenia or leukopenia. It increases the risk of infection.
  • A low platelet count is called thrombocytopenia. It increases the risk of bruising and bleeding.
  • A low red blood cell count is called anemia. It causes fatigue, paleness and a general feeling of discomfort or illness (called malaise).

Targeted therapy may affect the bone marrow’s ability to make blood cells, especially white blood cells and platelets. Drugs like bevacizumab (Avastin) can cause bleeding, including nosebleeds and blood in the stool or urine. Bleeding can make wounds heal more slowly. It can also increase the risk of other problems such as wound infection.

The healthcare team will take blood samples often to make sure blood cell counts stay within a normal range. If the levels go too low, targeted therapy may have to be stopped for a while to allow blood cell counts to return to normal.

Find out more about bone marrow suppression, low white blood cell count, low platelet count and anemia.


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Changes in blood pressure

Blood pressure may go too high or low depending on the targeted therapy drug given. Bevacizumab (Avastin) and aflibercept (Zaltrap) can cause high blood pressure.

Changes in blood pressure can cause dizziness, which should be reported to your healthcare team. Getting up slowly may help prevent dizziness.

Your healthcare team will check your blood pressure, especially when targeted therapy first starts. Sometimes the dose of a drug is changed to manage problems with blood pressure.

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Blood clots

Blood clots are a rare but serious side effect of some targeted therapy drugs. A blood clot in the leg is called a deep vein thrombosis (DVT). In the most serious cases, a blood clot can break off and travel to the lungs (called a pulmonary embolus, or PE). This can cause shortness of breath, coughing up blood, low oxygen levels in the blood and, potentially, heart failure.

Low doses of medicines that thin the blood may be given to help reduce the risk of blood clots. Tell your healthcare team if you have any redness, swelling, pain or cramps in the calf of the leg, shortness of breath or coughing up blood.


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Organ damage

Organ damage is a rare side effect of some targeted therapy drugs. The heart and lungs are the organs most likely to be damaged by targeted therapy drugs. Symptoms of heart and lung damage include swelling of the hands or feet, fast or uneven heartbeat, chest pain and shortness of breath or problems breathing.

Tell your doctor or healthcare team right away if you have these symptoms. They may lower the dose of the drug or stop giving the drug to prevent more damage to the heart or lungs.


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Allergic reactions

An allergic reaction (also called hypersensitivity) is not a common side effect of targeted therapy, but it can happen. Signs of an allergic reaction include difficulty breathing, wheezing, coughing and skin rash or hives. Allergic reactions are most likely to occur when targeted therapy drugs are given intravenously. They usually happen shortly after the drug is given.

Your healthcare team will monitor you closely for allergic reactions, especially when a targeted therapy drug is first given. Medicines and other treatments, such as oxygen therapy, are given if a severe allergic reaction occurs.

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Note: Details on specific drugs change quite regularly. Find out more about sources of drug information and where to get details on specific drugs.


Researcher Dr Michael Taylor Same brain tumour, different genetic profiles

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