DRUGS: SIDE EFFECTS OF CHEMOTHERAPY
Most current chemotherapy agents are cytotoxic, meaning that they function by killing dividing cells (see How Chemotherapy Drugs Work). Note that these chemotherapy agents do not specifically target cancer cells – but cancer cells by definition are cells that are dividing and growing out of control, so they are affected more than are normal cells. Some types of normal cells in the body also divide regularly, for instance, cells in the bone marrow, mucosal cells in the mouth and the lining of the intestines, and hair follicles. Most immediate side effects of chemotherapy are due to cytotoxic effects on these classes of normal cells. Some chemotherapy agents also effect specific organs (heart, bladder, kidneys, lungs) or the nervous system.
The sections below describe in some detail the different side effects of cytotoxic chemotherapy agents. The accompanying page on drugs used in the treatment of pediatric cancers lists which of these side effects are more likely to be experienced with each chemotherapy agent. Usually the side effects end when treatment ends.
SIDE EFFECTS DUE TO BONE MARROW SUPRESSION
Myelosuppression is the technical term for the suppression of the bone marrow’s production of blood cells: red blood cells, white blood cells, and platelets. Lowered levels of each of these types of blood cells lead to different side effects. Your child’s blood counts will be monitored periodically throughout treatment, and if some or all of the blood counts are too low, chemotherapy might be held until the counts come back up, or you might be advised to take special precautions to avoid infections or injuries.
Red blood cells. Low levels of red blood cells result in anemia. Red blood cells carry oxygen to all parts of the body, and when there are too few red blood cells, body tissues do not get enough oxygen. Anemia is characterized by tiredness, fatigue, weakness, paleness, heart palpitations, and shortness of breath.
White blood cells. White blood cells protect the body from invasion by pathogens, and when levels of specific types of these cells are low, a child has a lowered resistance to bacterial infection. The types of white blood cells that are important in fighting infections are called segs and bands. The absolute neutrophil count, or ANC, is a handy measurement of infection-fighting ability. ANC is the percentage of neutrophils (segs and bands added together) multiplied by the total white blood count. When the ANC falls below a certain level, the child is said to be neutropenic and precautions must be made to prevent infections. Neutropenia usually begins within a week after a chemotherapy treatment, and reaches its lowest point 2-3 weeks after treatment. Medicines called colony stimulating factors (CSF, or GCSF) help the recovery of white cells. These medicines are not generally given to patients with blood cancers such as leukemia.
Platelets. Low levels of platelets is called thrombocytopenia. Platelets help the blood to clot, thus preventing bleeding. Low platelets lead to easy bruising, nose bleeds, and excessive bleeding from wounds.
For more information on blood cells, blood counts, ANC, and neutropenia, see:
SIDE EFFECTS DUE TO DAMAGE TO CELLS LINING THE MOUTH
Chemotherapy can temporarily damage the normal cells lining the mouth (mucosal cells). This can lead to painful mouth sores, areas of inflammation and ulcers called stomatitis. Stomatitis usually starts about a week after chemotherapy and can last for several weeks. It can lead to infection and the inability to swallow food. Damage to the cells lining the mouth can lead to changes in taste. A food that your child used to love is now hated; something really strange (like hot candy) is now a favorite item. The Ped-onc resource center has information on remedies for mouth sores, as well as advice on mouth care in general during treatment.
SIDE EFFECTS DUE TO DAMAGE TO STOMACH, INTESTINE, AND ESOPHAGUS LININGS
Many chemotherapy agents will make your child experience nausea and vomiting due to cytotoxic effects on the cells in the digestive system. This generally begins within a short time after treatment is given and lasts for several hours. Modern drugs called anti-emetics (Zofran, Kytril) prevent or greatly reduce nausea.
Diarrhea is due to damage to cells lining the intestine. It can usually be easily controlled with medicine, but if it persists, your child might need IV fluids to replace lost fluid and nutrients.
Loss of appetite is sometimes a problem after chemotherapy. The dietitian at your hospital should be able to help with suggestions. If loss of appetite is extreme, your child will require a nasal gastrointestinal tube (NG tube) to supply needed nutrition.
Some chemotherapy agents are more likely than others to cause hair loss several weeks after starting treatment. Hair may thin or be lost completely. This hair loss is temporary, and the hair will regrow once the treatment ends.
NERVOUS SYSTEM EFFECTS
Chemotherapy can interfere with brain function, causing tiredness, confusion, and mood changes. Some patients or their parents refer to this as “chemo brain.” Some children experience depression after chemotherapy. In extreme and rare cases, damage to nerves inside and outside the brain can lead to seizures.
Some chemotherapy agents cause damage to the peripheral nervous system. Symptoms of peripheral neuropathy can include tingling, burning, weakness, numbness, and/or pain in the hands and feet, as well as weak or sore muscles.
EFFECTS ON ORGANS
Some chemotherapy agents are known to affect different body organs: the heart, bladder, kidneys, or lungs. Bladder and liver functions are followed by blood tests, while heart function is generally followed by echocardiograms. Damage to the lungs manifests as coughing or breathlessness. The doctors monitor organ damage carefully, and either hold chemotherapy or prescribe medications to counteract the affects.
Fatigue – feeling tired and lacking energy – is the most common symptom reported by cancer patients. The exact cause is not always known. It can be due to the cancer itself, chemotherapy, low blood counts, lack of sleep, pain, stress, poor appetite, along with many other factors.
Pain is a direct result of chemotherapy drugs that damage nerves, causing burning or shooting pain, most often in the fingers or toes. The mouth sores caused by some drugs are extremely painful. Other drugs cause headaches, muscle pains, or stomach pains. Your child’s oncologist can prescribe appropriate pain medications for any of these situation.
Some chemotherapy agents cause constipation. Like diarrhea, it can be controlled with medications.
A few chemotherapy drugs cause “gritty eyes”, due to inflammation of the lining of the eyelids. Your child’s oncologist can recommend soothing eye drops or other medications.
Skin and nails can be affected by different chemotherapy agents. Rashes, itching, peeling, dryness, acne, sun sensitivity, redness – all of these can be caused by chemotherapy. Some chemotherapy agents, when given by IV, cause the skin along the vein to darken. Nails can become yellow, brittle, and cracked, or show vertical lines.
Some chemotherapy agents cause raised levels of uric acid in the blood. A drug called allopurinol may be given to lower the uric acid levels.
Chemotherapy drugs can cause Syndrome of Inappropriate Antidiuretic Hormone Secretion, or SIADH, a condition of fluid and electrolyte imbalance. The symptoms of SIADH include weight gain, loss of appetite, nausea, vomiting, headache, muscle weakness/spasms/cramps, fatigue, abnormal mental status, and convulsions. See this Medline reference for more information.