Targeted Therapy: How Precision Cancer Medicines Work

This page is for people taking targeted therapy and their caregivers. It covers side effects people can have and when to call.

Targeted therapies act on specific proteins that cancer cells rely on to grow, divide, and spread. Some are pills you take at home. Others are given through a vein. ACS says healthy cells can also have some of these proteins. The normal cells most likely to be affected are skin and nail cells, hair follicles, cells in the mouth and digestive tract, and blood-forming cells in the bone marrow. NCI says the most common side effects include diarrhea and liver problems. Other possible effects include problems with blood clotting and wound healing, high blood pressure, fatigue, mouth sores, nail changes, and skin problems such as rash or dry skin.

Not everyone gets every side effect. Ask your team which ones are most common with your drug and when to call.

Rash is the most common skin change from targeted therapy. ACS says it often looks like acne and shows up on the scalp, face, neck, chest, and upper back. It is often worst within the first few weeks. Later the skin can crust and get very dry and red. It is not acne. Acne medicines do not work and can dry the skin out and make the rash worse.

Tell your care team right away about a rash, burning, or redness. ACS says creams, including steroids or antibiotics, may be used depending on the rash. Dry, cracked, or itchy skin can be helped with moisturizing or anti-itch creams. ACS also says your skin will likely become much more sensitive to light. It advises a hat, long sleeves, and a broad-spectrum sunscreen with SPF of at least 30.

Skin around the fingernails or toenails can become sore or red. Tell your team. Hair may thin. Eyelashes and eyebrows sometimes grow long enough to need trimming.

Some targeted drugs cause hand-foot syndrome. ACS says it usually starts during the first 2 to 6 weeks of treatment. The earliest signs are painful sensitivity, tingling, or numbness in the hands and feet. Then the palms and soles become red and swollen, like a sunburn, and may blister. The skin can also dry, peel, and crack.

What ACS suggests:

• wear well-fitting shoes and add insoles for padding
• wear thick, soft socks
• keep skin clean, cool, and dry
• do not pop blisters, because they can become infected

Tell your team as soon as your hands or feet start to hurt or change color. If a blister breaks on its own, contact your care team.

NCI says diarrhea is one of the most common side effects of targeted therapy. Ask before your first dose which antidiarrheal medicine you may take, at what dose, and when to stop it and call your care team instead.

ACS says to contact your care team right away for long-lasting diarrhea or vomiting, or for bloody stool. Also tell your team right away about dizziness when you stand, or passing less urine than usual. These can be signs of dehydration.

ACS says some targeted therapies, especially angiogenesis inhibitors, can raise blood pressure. Your doctor will watch your blood pressure closely. Some people need medicine to bring it down during treatment. Ask your team how often to check at home and what reading should make you call.

ACS says some of these drugs interfere with wound healing and usually need to be stopped before any planned surgery, including dental procedures. Tell any surgeon or dentist what you are taking. Talk to your cancer doctor as soon as you know about a planned procedure. Check with your doctor before adding any other medicine, vitamin, herb, or supplement. ACS says grapefruit juice can interfere with some targeted therapies.

Your team may pause a drug or change the dose to manage a side effect. ACS says doctors try to give targeted therapy at levels high enough to treat cancer while keeping side effects at a minimum.

Do not stop or reduce a tablet on your own. Call, describe what is happening, and let your team decide. That way your record matches what you actually took.

• Call 911 or go to the nearest emergency department if you have chest pain, sudden shortness of breath or trouble breathing, weakness on one side, trouble speaking, seizures, or swelling of the lips, tongue, or throat. ACS says these can be signs of serious problems such as blood clots or an allergic reaction. Do not drive yourself.
• Call 911 or go to the nearest emergency department for bleeding that will not stop, black or tarry stool, blood in vomit or vomit that looks like coffee grounds, sudden confusion, or being hard to wake. Do not drive yourself.
• Call 911 or go to the nearest emergency department if severe belly pain comes on. NCI notes that very rarely, a hole can form through the wall of the esophagus, stomach, small intestine, large bowel, rectum, or gallbladder. ACS says to tell your doctor right away about any belly pain or vomiting. Do not drive yourself.
• Call your care team right away, day or night, if you have a fever, intense chills, bleeding or unexplained bruising, a rash, pain or soreness at an injection or catheter site, unusual pain including intense headaches, long-lasting diarrhea or vomiting, or bloody stool or blood in your urine. ACS lists all of these as reasons to contact your team right away.
• If you are also on chemotherapy or have low white blood cells, call your care team right away, day or night, for a temperature of 100.4 degrees F (38 degrees C) or higher, chills, a sore throat, mouth sores, burning when you urinate, redness at a catheter site, or any other sign of infection. Do this even if your temperature is normal.
• Call your care team right away if the palms or soles blister or become painful, or if home blood pressure readings sit above the number your team gave you.

• NCI: Targeted Therapy to Treat Cancer
• American Cancer Society: Targeted Drug Therapy Side Effects
• American Cancer Society: Hand-Foot Syndrome