Chemotherapy (chemo) is the use of strong medicines to treat cancer. It has been used for many years and is one of the most common treatments for cancer. In most cases, chemo damages the cancer cell's ability to grow and spread. Different groups of medicines work in different ways to fight cancer.

Chemo may be used alone for some types of cancer. Or it may be given with other treatments, such as radiation or surgery. Chemo may also be used along with other cancer medicine treatments, such as targeted therapy, hormone therapy, or immunotherapy. Often a combination of chemo medicines is used to treat a certain type of cancer. These combinations are given in a certain order.

Chemo can work well to treat certain cancers. But chemotherapy medicines travel to most parts of the body, not just the cancer cells. So healthy cells can be damaged, too. This can lead to side effects during treatment. Knowing what these side effects are and that they can happen can help you and your caregivers prepare for and manage them.

Your doctor may suggest chemo for any of these reasons:

• Alone, as the sole treatment. Some cancers are treated right away with chemo only.
• Before surgery or radiation. It helps to shrink the tumor so that it's smaller and easier to take out or treat with radiation. This is called neoadjuvant chemotherapy.
• During radiation. This is called concurrent chemoradiation. The chemo helps the radiation work better.
• After surgery or radiation. It helps keep any cancer cells that are left from growing and spreading. This is called adjuvant chemotherapy. Whether your doctor suggests it depends on the tumor's size, if it has spread, and other features.
• When the cancer has spread to other parts of your body. Because chemo travels all over the body to kill cancer cells, it can be used to kill cancer cells that have spread.
• To ease problems caused by the cancer. The chemo isn't expected to cure the cancer, but can ease problems. For instance, it may shrink a tumor that's pressing on a nerve and causing pain. This is called supportive or palliative care.

Chemo can be given in any of these ways:

• As a pill, capsule, or liquid you swallow (orally)
• As a shot (injection) into the muscle or fat tissue
• Directly into the blood of a vein (by I.V. or intravenously)
• Applied as a cream or gel onto the skin (topically)
• Directly into a body cavity, such as the belly (intracavitary or intraperitoneal chemo)
• Into the fluid-filled space between layers of tissue that cover your brain and spinal cord (intrathecal or IT)
• Directly into the bladder for a short time (intravesical)
• Into a main artery that "feeds" the tumor (intra-arterial)
• Through a needle into the tumor (intralesional)

Chemo is usually given in cycles to reduce the damage to healthy cells. It also gives the cells a chance to recover. Each cycle includes a time of treatment and a time of rest with no treatment. Cycles allow the medicines to kill more cancer cells because not all of the cells are dividing at the same time. The rest period gives the healthy cells in your body time to recover and heal. Chemo may be given daily, weekly, every few weeks, or monthly.

Chemo is often given in an outpatient setting. This may be a hospital, clinic, infusion center, or doctor's office. People getting chemo will be watched for reactions during treatments. Since each treatment session may take a while, you are encouraged to bring along something that is comforting, such as music to listen to. It's also advised to bring something to help pass the time, such as a laptop or a book. Since it's hard to predict how you will feel after chemo, it's important to have someone drive you to and from the treatment the first few times.

Many different kinds of chemo medicines are used to treat cancer. Nearly all of them cause side effects.

Side effects may happen during, just after, or weeks after treatment (in minutes, hours, days, or weeks). Or they may happen months or even years later after chemo has been given. Side effects may range from severe to mild, or be absent. Each person's medical history, overall health, and diagnosis is different. So is the reaction to treatment.

Side effects depend on the chemo medicines used, dose, and the combinations used. Before treatment starts, talk with your cancer care team about the possible side effects of your treatment. Ask about each medicine's side effects. Get written information on each medicine you're getting so you know what to watch for and what to report to your doctor.

Some of the most common short-term side effects include:

• Extreme tiredness (fatigue)
• Increased risk for infection
• Easy bruising and bleeding
• Mouth and throat sores
• Nausea and vomiting
• Diarrhea
• Constipation
• Hair loss
• Skin and nail changes
• Nerve damage, such as numbness or tingling, usually in your feet and sometimes hands
• Decreased or no desire to eat
• Weight gain or loss
• Changes in your memory or thinking

Possible long-term side effects include:

• Not able to have children (infertility)
• Memory or thinking changes
• Damage to certain organs, such as your heart, bladder, or lungs
• Increased risk for other kinds of cancer

Many of the short-term side effects can be controlled or even prevented. Most may get better during the rest part of the chemo cycle. They often go away over time after treatment is done.

It's important to know which medicines you're taking. Write your medicines down. Ask your health care team how each medicine works and what side effects each medicine might have—both short-term and long-term. Talk about the goal of your chemo treatment. Your cancer care team is the best place to get information. They can tell you how chemo will be given, what you can expect it to be like, and how long you will get treatment.

Also talk with your doctors about what problems to look for and when to call them. Make sure you know what number to call with questions. Is there a different number for evenings, holidays, and weekends?

There's no way to tell if you will have side effects from chemo, which side effects you will have, or how bad they will be. Knowing what to watch for and what to do if you have problems is a good way to be prepared. It may be helpful to keep a diary of your side effects. Write down any physical, thinking, and emotional changes. A written list will make it easier for you to work with your health care team to make a plan to manage your side effects. It will also help you remember your questions when you go to your appointments.