Chemotherapy (chemo) uses anticancer medicines to kill cancer cells. The medicines are made to attack and kill cancer cells that grow quickly. Some normal cells also grow quickly. Because of this, chemo can also harm those cells. This can cause side effects.

Chemo can help treat stomach cancer in several ways:

• It can shrink the cancer before surgery. This can help make the cancer easier to remove. Chemo that is given before surgery may be called neoadjuvant therapy.
• It can destroy any cancer cells that remain after surgery. In this case, it's often used with radiation therapy. It may be called chemoradiation. Treatment after surgery may be called adjuvant therapy. It might help keep the cancer from coming back.
• It can destroy stomach cancer cells that have spread. Sometimes stomach cancer cells spread to other parts of the body. This is called metastasis. Chemo may then be the main treatment. It goes all over your body in your blood. It can kill or slow the growth of cancer cells that have spread beyond your stomach.

There are many different kinds of chemo. Each works in a different way. Some are taken by mouth. Most are given in a vein through an I.V. (intravenous) line.

The three most common medicines used to treat stomach cancer include:

• Fluorouracil (I.V.) or capecitabine (by mouth) (may be given with leucovorin).
• Oxaliplatin.

Other chemo medicines for stomach cancer include:

• Irinotecan.
• Carboplatin.
• Epirubicin.
• Cisplatin.
• Paclitaxel.
• Docetaxel.
• Trifluridine and tipiracil.

Most people get chemo in an outpatient setting at a hospital, doctor's office, or clinic. You likely won't need to stay overnight.

In most cases, at least two different chemo medicines are used at the same time. They might also be used alone or combined with targeted therapy. You'll get chemo in cycles that last a few weeks. You'll get the chemo for a few days with rest periods in between. This gives your body time to recover between treatments.

Chemo attacks normal cells as well as cancer cells. This can cause side effects. The side effects you have depend on the amount and type of chemo you get. Talk with your doctors about what to expect with your chemo.

Side effects may occur in the days or weeks while you're getting chemo. After your treatment ends, the side effects often go away over time. But they may continue long term. Different chemo medicines have different side effects. Some common side effects include:

• Nausea and vomiting.
• Loss of appetite.
• Sores in the mouth.
• Diarrhea.
• Tiredness.
• Infections.
• Bruising and bleeding more easily than normal.
• Hair loss.
• Nerve pain, tingling, or numbness in hands or feet (peripheral neuropathy).

Talk with your doctors about any side effects you have. There are often ways to manage or even prevent side effects.

It's important to know which chemo medicines you're getting. Write down the names of all your medicines. Ask your care team how they work and what short- and long-term side effects they might cause.

Talk with your doctors about what signs to look for and when to contact them. For example, chemo can make you more likely to get infections. Make sure you know the best way to contact your doctors with questions or problems. Is there a different number to use when the clinic is closed on evenings, weekends, and holidays?

It may be helpful to keep a diary of your side effects. Write down physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your care team to make a plan to manage your side effects.