Immunotherapy for Colorectal Cancer
Immunotherapy is the use of medicines to help a person’s own immune system better recognize and destroy cancer cells. 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 the body's normal cells. 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 keep the immune system from attacking them. But drugs that target these checkpoints hold a lot of promise as cancer treatments.
Drugs called checkpoint inhibitors can be used for 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 drugs are used for people whose cancer is still growing after treatment with chemotherapy. They might also be used to treat people whose cancer can't be removed with surgery, has come back (recurred) after treatment, or has spread to other parts of the body (metastasized).
Pembrolizumab (Keytruda) and nivolumab (Opdivo) are drugs that target PD-1, a protein on immune system cells called T cells that normally help keep these cells from attacking other cells in the body. By blocking PD-1, these drugs boost the immune response against cancer cells.
These drugs are given as an intravenous (IV) infusion every 2 or 3 weeks.
Side effects of these drugs can include fatigue, cough, nausea, itching, skin rash, decreased appetite, constipation, joint pain, and diarrhea.
Other, more serious side effects occur less often. These drugs work by basically removing the brakes from 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.
Ipilimumab (Yervoy) is another drug that boosts the immune response, but it has a different target. It blocks CTLA-4, another protein on T cells that normally helps keep them in check.
This drug can be used along with nivolumab (Opdivo) to treat colorectal cancer, but it’s not used alone. It is given as an intravenous (IV) infusion, usually once every 3 weeks for 4 treatments.
The most common side effects from this drug include fatigue, diarrhea, skin rash, and itching.
Serious side effects seem to happen more often with this drug than with the PD-1 inhibitors. Like the PD-1 inhibitors, this drug can cause the immune system to attack other parts of the body, which can lead to serious problems in the intestines, liver, hormone-making glands, nerves, skin, eyes, or other organs. In some people these side effects can be life threatening.
It’s very important to report any new side effects during or after treatment with any of these drugs to your health care team promptly. If serious side effects do occur, you may need to stop treatment and take high doses of corticosteroids to suppress your immune system.