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Immunotherapy for Stomach Cancer

Immunotherapy is the use of medicines to help a person's own immune system find and destroy cancer cells more effectively.

Immune checkpoint inhibitors

An important part of the immune system is its ability to prevent itself from attacking normal cells in the body. To do this, it uses “checkpoint” proteins on immune cells, which act like switches that need to be turned on (or off) to start an immune response. Cancer cells sometimes use these checkpoints to avoid being attacked by the immune system.

Drugs that target these checkpoints (called immune checkpoint inhibitors) can be used to treat some people with stomach cancer (also known as gastric cancer).

PD-1 inhibitors

Nivolumab (Opdivo) and pembrolizumab (Keytruda) are drugs that target PD-1, a protein on immune system cells called T cells. The PD-1 protein normally helps keep T cells from attacking other cells in the body. By blocking PD-1, these drugs boost the immune response against cancer cells. This can shrink some tumors or slow their growth.

Nivolumab can be used in people with advanced stomach cancer, typically along with chemotherapy.

This drug is given as an intravenous (IV) infusion, usually once every 2 or 3 weeks.

Pembrolizumab can be used as part of the first treatment for people with advanced stomach cancer, either:

This drug can also be used after other treatments including chemotherapy have been tried, and if the cancer cells test positive for any of the following:

  • A high level of microsatellite instability (MSI-H) or a defect in a mismatch repair gene (dMMR)
  • A high tumor mutational burden (TMB-H), meaning they have many gene mutations

This drug is given as an intravenous (IV) infusion, typically once every 3 or 6 weeks.

Possible side effects

Side effects of these drugs can include:

  • Feeling tired or weak
  • Fever
  • Cough
  • Nausea
  • Itching
  • Skin rash
  • Loss of appetite
  • Muscle or joint pain
  • Shortness of breath
  • Constipation or diarrhea

Other, more serious side effects occur less often. These can include:

Infusion reactions: Some people might have an infusion reaction while getting one of these drugs. This is like an allergic reaction, and can include fever, chills, flushing of the face, rash, itchy skin, feeling dizzy, wheezing, and trouble breathing. It’s important to tell your doctor or nurse right away if you have any of these symptoms while getting one of these drugs.

Autoimmune reactions: These drugs work by basically removing one of the safeguards on the body’s immune system. Sometimes this causes the immune system to attack other parts of the body, which can lead to serious or even life-threatening problems in the lungs, intestines, liver, hormone-making glands, kidneys, skin, or other organs.

It’s very important to report any new side effects to your health care team right away. If serious side effects do occur, treatment may need to be stopped and you may get high doses of corticosteroids to suppress your immune system.

More information about immunotherapy

To learn more about how drugs that work on the immune system are used to treat cancer, see Cancer Immunotherapy.

To learn about some of the side effects listed here and how to manage them, see Managing Cancer-related Side Effects.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

Bendell J, Yoon HH. Progressive, locally advanced unresectable, and metastatic esophageal and gastric cancer: Approach to later lines of systemic therapy. UpToDate. 2020. Accessed at on July 13, 2020.

Ku GY, Ilson DH. Chapter 72: Cancer of the Stomach. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, Pa: Elsevier; 2020.

National Cancer Institute. Physician Data Query (PDQ). Gastric Cancer Treatment. 2020. Accessed at: on July 13, 2020.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Gastric Cancer. Version 2.2020. Accessed at on July 13, 2020.

Last Revised: November 21, 2023

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