Immunotherapy for Colorectal Cancer

Immunotherapy is the use of medicines to help a person’s own immune system recognize and destroy cancer cells more effectively. Immunotherapy can be used to treat some people with advanced colorectal cancer.

Immune checkpoint inhibitors

An important part of the immune system is its ability to keep itself from attacking normal cells in the body. To do this, it uses “checkpoint” proteins on immune cells, which act like switches needing 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. But drugs that target these checkpoints hold a lot of promise as cancer treatments.

Pembrolizumab (Keytruda) is a drug that targets PD-1, a protein on immune system cells called T cells that normally helps keep these cells from attacking other cells in the body. By blocking PD-1, this drug boosts the immune response against cancer cells. This can shrink some tumors or slow their growth.

This drug is only helpful in people whose colorectal cancer cells have tested positive for specific gene changes, such as a high level of microsatellite instability (MSI-H), or changes in one of the mismatch repair (MMR) genes. The drug is used in people whose cancer is still growing after treatment with chemotherapy.

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

Possible side effects

Side effects can include fatigue, fever, cough, shortness of breath, itching, skin rash, nausea, loss of appetite, diarrhea, constipation, and muscle or joint pain.

Other, more serious side effects occur less often. Checkpoint inhibitors work by basically removing the brakes on the body’s immune system. Sometimes the immune system starts attacking other parts of the body, which can cause serious or even life-threatening problems in the lungs, intestines, liver, hormone-making glands, kidneys, or other organs.

It’s very important to report any new side effects to your health care team promptly. 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.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

US Food and Drug Administration. FDA approves first cancer treatment for any solid tumor with a specific genetic feature. [News Release] 2017. Accessed at https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm560167.htm on May 24, 2017.

Last Medical Review: May 24, 2017 Last Revised: May 24, 2017

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