Understanding The Side Effects Of Cancer Treatment

Fear about side effects from cancer treatment adds to the stress of a cancer diagnosis. This fear comes from a belief that the discomfort they cause cannot be relieved, but that is not true. Many advances have been made in preventing or managing the most common treatment-related side effects. Managing these effects is important because if you feel better, you are more likely to complete your treatment as planned by your oncologist, and treatment is most effective when it is carried out as planned. Learning the facts about side effects can help you better cope with them.

Side effects differ in many ways

The side effects of cancer treatment can vary. First, not all people will have the same side effects. A friend or relative may have had a certain side effect after treatment, but that does not mean you will experience the same side effect. Whether or not a side effect occurs depends on many factors, including your age, your overall health, your specific cancer and your specific treatment plan.

Side effects differ in how serious they are. Some cause minor inconvenience or discomfort, and others may cause more discomfort, pain and/or emotional distress. Occasionally, a serious side effect may require immediate medical attention. It is important to know that there are ways to relieve the discomfort of most treatment-related side effects and to prevent them from becoming severe. It is also important to know when you should call your doctor about symptoms related to side effects.

Side effects also differ according to when they occur. Those that occur during treatment are called short-term (or acute) side effects. Short-term effects usually disappear once treatment ends. In contrast, long-term side effects may not completely disappear until months or years after treatment has ended. The last category of side effects is late effects, which occur less frequently than short-term or long-term effects. Late effects do not occur during treatment; rather, they occur at least six months after treatment has been completed.

The most important way in which side effects differ is according to the type of cancer treatment – surgery, radiation therapy, chemotherapy, hormone therapy or targeted therapy. Many people with cancer receive a combination of treatments, which may increase the possibility of side effects.

Types of cancer treatment and their side effects

Sometimes one treatment is best for a cancer, and other times two or more treatment options offer similar outcomes. Your oncologist will talk to you about the treatment options for your particular cancer. You should learn all you can about side effects by asking your oncologist some specific questions when discussing treatment options (see "Questions to ask your doctor..." at bottom of page).


When possible, surgery is done to remove a cancerous tumor, and lymph nodes in the area of the tumor are also usually removed (to see if cancer has spread to the nodes). The side effects of surgery may be short-term or long-term and vary according to the area of the body where the surgery was done (Table 1). Most people have some level of pain after surgery and will usually need to limit activities in the first few days or weeks after surgery. People recover at different rates depending on their age, general health and the location of the tumor. Surgery causes scars, may affect bodily functions and may change your body’s appearance, and there may also be tissue swelling around or near the site of surgery. These changes may affect how you feel about your body image.

Radiation therapy

With radiation therapy, beams of radiation are delivered from a machine to the part of the body where the tumor is located. The radiation shrinks the tumor by destroying cancer cells. Much care is taken to ensure the radiation is delivered precisely to the tumor to avoid damaging nearby normal cells. However, normal cells in the pathway to the tumor may still be affected.

Because radiation is delivered through the outside of the body, the skin and underlying tissues in the area being treated may become sensitive. This sensitivity is short-term and usually resolves gradually within two months after treatment has been completed. There may be short-term or long-term swelling or scarring of the tissues in the area; scarred tissues may become firm or contracted. Other side effects vary according to the part of the body being treated and may be short-term or long-term or may occur late after treatment (Table 1).


Chemotherapy involves the use of very strong drugs that kill cancer cells throughout the body, but these drugs can also damage normal, healthy cells, which may cause side effects. The normal cells most often affected are the blood-forming cells in the bone marrow as well as hair follicles and cells lining the inside of the mouth and digestive tract. Many side effects of chemotherapy are short-term (Table 1). Problems with thinking, remembering and understanding, known as “chemo-brain,” may be long-term effects. Some drugs have also been associated with late effects.

Hormone therapy

Hormone therapy is sometimes used to slow or stop the growth of prostate cancer in men and to prevent the recurrence of some types of breast cancer in women. Hormone therapy acts by decreasing the amount of hormones made naturally in the body. For men, hormone therapy decreases the level of testosterone; for women, hormone therapy decreases the levels of estrogen and progesterone, causing side effects that are similar to the symptoms of menopause (Table 1). Although the side effects of hormone therapy in both men and women usually disappear when treatment ends, hormone therapy is typically given for a long period of time. This means that a side effect may be experienced for many months or years.

Targeted therapy

Targeted therapy is the use of drugs or biologic substances that stop or slow cancer growth by interfering with specific molecules in the body involved in the process of creating cancer cells. Because targeted therapy is designed to attack specific cells, it is less harmful to normal cells than traditional chemotherapy. However, some side effects may occur (Table 1). As with hormone therapy, targeted therapy may last for a long period of time, so even short-term effects may be present for many months. Targeted therapy is the newest approach to treating cancer, and not enough information has been collected to clearly understand late effects.

Table 1. Most common side effects based on type of treatment

Type of treatment Short-term side effects Long-term side effects Late effects
    (depending on
    the site of
▪ Pain
▪ Limited mobility
    and/or activities
▪ Slow digestion
▪ Scars
▪ Impaired wound
▪ Chronic pain
▪ Change in function
▪ Negative body image
▪ Lymphedema
▪ Phantom limb
    sensation (if part of
    limb is removed)
Radiation therapy
    (depending on
    the site of
▪ Skin sensitivity
    (redness, dryness,
    peeling, itchiness)
▪ Fatigue
▪ Anemia
▪ Hair loss (in the area
    of the body being
▪ Nausea and vomiting
    (if abdomen is
▪ Mouth sores (if head or
    neck is radiated)
▪ Headache (if head is
▪ Fatigue
▪ Dry mouth
▪ Loss of or changes in
    taste (if head or neck
    is radiated)
▪ Problems with thinking,
    memory (if brain is
▪ Loss of motion in joints
    (if limb or joint is
▪ Infertility (if abdomen is
▪ Cavities and tooth
    decay (if head is
▪ Lymphedema
▪ Nausea and vomiting
▪ Neutropenia (which
    increases risk of
▪ Anemia
▪ Fatigue
▪ Changes in appetite
▪ Hair loss
▪ Mouth sores
▪ Diarrhea
▪ Skin and nail changes
▪ Fatigue
▪ Menopausal
▪ Nerve problems
    (known as
    peripheral neuropathy)
▪ “Chemo-brain”
    (forgetfulness or
    trouble concentrating)
▪ Heart problems
▪ Cataracts
▪ Infertility
▪ Heart failure
▪ Abnormal liver function
▪ Osteoporosis
Hormone therapy*
▪ Hot flashes
▪ Constipation or
▪ Nausea
▪ Dizziness, headache
▪ Trouble sleeping
▪ Impotency, decreased
    sex drive
▪ Weight gain
▪ Fatigue

▪ Hot flashes
▪ Vaginal discharge and
▪ Joint pain
▪ Muscle aches
▪ Headache
▪ Depression
▪ Increased risk of bone
▪ Increased risk of blood
▪ Cancer of the uterus
▪ Bone loss

Men and women:
▪ Increased risk of blood
Bone loss
Targeted biologic therapy
▪ Acne-like rash
▪ Increased risk of
▪ Flu-like syndrome
▪ Dry, itchy skin
▪ Nausea/vomiting 
▪ Slow-growing, brittle
▪ Diarrhea/constipation
▪ Mouth sores
▪ Anorexia
▪ Increased risk of blood
▪ Growth of eyelashes;
    discomfort in eyes or
▪ Fatigue
▪ Heart problems
▪ Increased risk of blood
▪ Neutropenia (which
    increases risk of
▪ Fatigue
▪ High blood pressure
▪ Heart problems
▪ Cardiac toxicity
    (damage to muscles
    of the heart
*Hormone therapy is typically given for a long period of time, so short-term side effects may last for a long period of time.

Importance of learning about side effects

It is not possible to predict how each individual will be affected by cancer treatment, but talking with your health care team can better prepare you for what may happen. This information will help you learn more about side effects, how they can be managed, and how to talk to your doctor about them. It provides overviews of the most common treatment-related side effects and includes lists of resources to help you find more information. Learn as much as you can. Knowing what to expect and how to help prevent or manage side effects can help you feel in control of your body, improve your quality of life, and, most importantly, ensure that you have the best chance for treatment to be effective.

Questions to ask your doctor when discussing treatment options

  • What are the possible side effects of each of my treatment options?
  • How common are these side effects?
  • When are these side effects most likely to occur?
  • How do the benefits of the recommended cancer treatment compare with the risks?
  • How long will the side effects probably last?
  • Is there a way to decrease the possibility that these side effects will occur?
  • Are there medications available to relieve or prevent these side effects?
  • How will I be monitored for long term side effects such as heart problems?
  • When should I contact a member of my health care team about a side effect?
  • Whom should I call?

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