Why chemotherapy causes side effects
Chemotherapy is designed to slow actively growing cancer cells; however,
these drugs do not distinguish between an actively growing cancer cell
and an actively growing healthy body cell. Side effects occur when the
chemotherapy disrupts the healthy cells that maintain the body's
appearance and function. Many patients experience side effects, but many
of these unintended problems can be managed and disappear once
chemotherapy is completed.
Side effects are often treatable, and you are encouraged to talk with
your doctor if you experience any side effects. It is important to
understand that chemotherapy is easier to tolerate today than even a few
years ago. Experiencing side effects does not mean the treatment is
working better. Similarly, the absence of side effects does not mean that
the treatment is not working. Furthermore, chemotherapy can be very
effective in treating cancer and relieving cancer symptoms and the
potential of side effects should not deter a patient from getting
Common side effects of chemotherapy
Different drugs cause different side effects. Although specific side
effects may be predictable for certain classes of drugs, each person's
overall experience with chemotherapy is unique. Talk with your doctor
about side effects, so they can be promptly treated or better managed.
For more information, read the Managing Side Effects of Cancer Treatment
Chat Transcript and PLWC's Managing Side
With chemotherapy, a patient may experience one or more of the following
side effects. Some people do not experience any treatment side effects.
Hair loss. Patients receiving chemotherapy may lose hair
throughout their body. After a few chemotherapy treatments, hair may
begin to fall out gradually or in clumps. Fortunately, hair loss from
chemotherapy is almost always temporary.
Nausea and vomiting. Many patients associate chemotherapy with
nausea and vomiting, but new medications can minimize or prevent these
side effects in the majority of people. Sometimes patients experience
delayed vomiting (vomiting up to 24 hours after treatment) or
anticipatory vomiting (vomiting before the next treatment after a bad
experience from the first treatment). Talk with your doctor if you
experience either of these side effects.
Diarrhea. Loose or watery bowel movements occur in three out of
four people who receive chemotherapy because of the damage to rapidly
dividing cells in the gastrointestinal (digestive) tract. Untreated diarrhea
can be serious and even life threatening if it leads to dehydration and
malnutrition (poor nutrition from an improperly balanced diet). Tell your
doctor if you experience diarrhea, so treatment can begin promptly.
Constipation. Patients receiving chemotherapy may develop
constipation, the infrequent or difficult passage of stool. Often, pain
medications cause constipation. Also, patients sometimes unknowingly
increase their risk of constipation by not drinking enough fluids, eating
balanced meals, or getting enough exercise. Talk with your doctor about
ways to relieve the symptoms of constipation.
Fatigue. The most common chemotherapy symptom reported by patients
is fatigue, or feeling tired and lacking energy. Chemotherapy may cause
or increase fatigue, so plan your days to include short naps and light
exercise to help increase your energy levels. For more information, read
the PLWC Feature: Coping With Cancer-Related Fatigue.
Sores in the mouth and throat. Chemotherapy can cause sores to
develop in the mouth or throat by damaging the cells that line these
areas. The sores usually develop five to 14 days after receiving
chemotherapy and often heal completely when treatment is completed.
Patients getting chemotherapy who have poor
diets and/or dental hygiene increase their risk of mouth and throat
sores, which, in turn, increases the risk of serious infections.
Blood disorders. Chemotherapy affects production of new blood
cells from the bone marrow, the spongy, red tissue in the inner part of
bones. Your doctor will monitor the levels of red blood cells (RBCs) and white blood cells (WBCs)
using a test called a complete blood count (CBC). Low RBCs
result in anemia, which decreases the body’s ability to carry oxygen
throughout the body. As a result, you may feel fatigued, dizzy, or short
of breath. A lower than normal number of WBCs,
or leukopenia, increases your risk of
infections. A second type of test, called a platelet count, measures the
number of platelets in your blood. Thrombocytopenia, a shortage of
platelets, reduces your blood’s ability to clot and you may bleed or
bruise more easily. Your doctor can treat all three of these deficiencies
using newer medications that stimulate the bone marrow to make more
blood-forming cells that develop into RBCs, WBCs, and platelets.
Nerve and muscle effects. Some chemotherapeutic drugs cause nerve
and muscle damage, resulting in one or more of the following symptoms:
- Weakness or numbness in
the hands and/or feet
- Weak, sore, tired, or achy
- Loss of balance
- Shaking or trembling
- Stiff neck
- Visual problems
- Walking problems
- Hearing difficulties
These symptoms usually decrease when the chemotherapy dose
is lowered or treatment is stopped; however, in some cases, the damage is
Changes in thinking and memory. Some patients getting chemotherapy
may describe their minds as being in a fog—unable to concentrate, find
the right word, or remember things, such as where they put their keys.
This experience of "chemobrain" or
"chemofog" is subtle but can be
troublesome to those who experience it. Programs to improve memory and
problem-solving abilities help to reverse these side effects, but some
people have persistent difficulties with certain mental tasks even after
chemotherapy is completed. For more information, read CancerCare's
Chemobrain Information Series: Cognitive
Problems After Chemotherapy.
Reproductive and sexual issues. Chemotherapy can have an effect on
reproduction and sexuality. Discuss any concerns with your doctor before
treatment begins. During treatment, men are encouraged to use condoms
during sexual intercourse for the first 48 hours after chemotherapy
because some of the drug(s) may end up in the sperm. Because some types
of chemotherapy cause genetic changes in sperm or eggs that could lead to
birth defects, both men and women are encouraged to use birth control
throughout their treatment. For more information, read PLWC's Sexuality
Reproductive and sexual issues for men. Chemotherapy may cause
temporary or permanent infertility (inability to father a child). Those
who wish to have children after chemotherapy can consider freezing their
sperm for future use. Impotency (inability to perform sexually) due to
chemotherapy is rare, but certain drugs may affect erections and sexual
desire by reducing the amount of testosterone produced. A few
chemotherapeutic drugs permanently damage parts of the nervous system and
may play a role in impotency by injuring the nerves that control
Reproductive and sexual issues for women. Chemotherapy can damage
the ovaries and result in temporary or permanent infertility. However,
birth control is important even if your periods are irregular or absent;
pregnancy could interfere with your cancer treatment and/or the baby's
development. Depending on your age and the drugs used, chemotherapy can
also lead to early menopause, which may be temporary or permanent. Tissue
changes associated with menopause can make intercourse uncomfortable and
bladder and/or vaginal infections more likely.
Appetite. Loss of appetite during chemotherapy can seriously
affect a patient's ability to regain health. Without proper nutrition,
the body cannot recover as well from the damage caused by chemotherapy.
Patients who maintain their weight cope with side effects and fight
infections better. If you feel too tired to eat, have lost your appetite,
or have mouth or throat problems that make it difficult or painful to
eat, your doctor may recommend that you be given nutrition intravenously
until you are able to eat again. You may also ask your doctor to
recommend a dietitian who can help you to maintain your weight.
Pain. Chemotherapy can cause pain, including mouth sores,
headaches, muscle pains, and stomach pains, as well as burning, numbness,
or shooting pains (most often in the fingers and toes) from nerve damage.
Not everyone who receives chemotherapy experiences pain. For those who
do, it's important to know that most pain can be relieved. It is helpful
if you can describe for your doctor where you feel pain, what it feels
like (sharp, dull, throbbing, or steady), how strong it is, how long it
lasts, and what kinds of things reduce or increase its intensity. For
more information, read PLWC Feature: Cancer Pain.
Long-term side effects. Chemotherapy side effects usually
disappear at the end of treatment. However, side effects may recur or develop
later. Certain types of chemotherapy are associated with permanent organ
damage to the heart, lung, liver, kidneys, or reproductive system.
Cognitive (thinking, concentrating, memory)
issues remain for some people, and children who have received chemotherapy
for cancer treatment may have development problems. Nervous system
changes can develop months or years after treatment. Finally, cancer
survivors have a higher risk of developing second cancers. Follow-up care
is an essential component of health care for all cancer survivors. For
more information, read the 2004 Meet the Expert Cancer Advances:
Survivorship—Increasing Survival, Improving Lives and the Institute of Medicine
Cancer Survivorship Report: From
Cancer Patient to Cancer Survivor: Lost in Transition.
National Cancer Institute (NCI): Chemotherapy and You: A Guide to
Self-Help During Cancer Treatment
CancerCare: Understanding and Managing
Chemotherapy Side Effects booklet based on an April 2005 Telephone
Mayo Clinic: Chemotherapy: Using chemicals to treat cancer
Mayo Clinic: Chemobrain: When cancer treatment
disrupts your thinking and memory skills
American Cancer Society (ACS): What Are the Possible Side Effects of
ACS: Side Effects of Chemo on Reproduction and Sexuality in Men
ACS: Side Effects of Chemo on Reproduction and Sexuality in Women
ACS: How Do I Deal With Losing My Hair?
ACS: Some Cancer Doctors Underestimate Chemotherapy Side Effects
BreastCancer.org: Managing Chemo Side Effects
BreastCancer.org: Ask-the-Expert Conference: Chemotherapy Updates