Back to
Updated on August 19, 2025
The body's immune system has natural defenses against cancerous cells. However, cancers have ways of evading detection by the immune system, weakening the immune system, and growing too quickly for the immune system to keep up.
Immunotherapy is a category of cancer treatments that help the immune system detect and attack cancerous cells. Immunotherapies have become an important tool in the treatment of many types of cancer, including many instances of colorectal cancer, cancer that originates in the large intestine (a digestive organ that consists of the colon and rectum).
The immunotherapies used for the treatment of colorectal cancer are called immune checkpoint inhibitors.
Most immune checkpoint inhibitors are given as intravenous (IV) infusions, delivered directly into the bloodstream with a needle inserted into a vein. A new and emerging approach to delivering immunotherapy is subcutaneous injections, which are administered into a layer of tissue under the skin.
While options for subcutaneous immunotherapy are limited at the moment, they are expected to expand in the future.
If you or a loved one is living with colorectal cancer, here are a few things to know about immunotherapy and subcutaneous immunotherapy.
When is immunotherapy used to treat colorectal cancer?
Surgery, ablation, radiation therapy, chemotherapy, targeted therapy, and immunotherapy are all used in the treatment of colorectal cancer. A treatment plan will often include a combination of different therapies.
As with any type of cancer, there is no specific treatment that is best in all cases. Each person has unique treatment needs. Treatment for colorectal cancer will depend on multiple factors, including:
- The type and location of the cancer, including whether it began in the colon or rectum
- The stage of the cancer, including the size of the tumor, if the cancer has spread, and where the cancer has spread
- The results of molecular testing, tests that detect certain genes, proteins, or molecules that can help guide treatment (especially in metastatic disease)
- A person's age, overall health (including any coexisting health conditions), and their preferences about treatment
Molecular testing is a deciding factor in whether immunotherapy is a treatment option. Specifically, molecular testing that looks for gene changes called microsatellite instability (MSI) and changes in mismatch repair (MMR) genes. These changes result in the production of large numbers of abnormal proteins called neoantigens.
Neoantigens are a good target for the immune system’s natural defenses against cancerous cells. However, the immune system may need help recognizing these cells as being cancerous, which is where immunotherapy can help.
Immune checkpoint inhibitors
Immune checkpoints are proteins that prevent the immune system from attacking cells. Normally, immune checkpoints prevent the immune system from attacking healthy cells. Cancerous cells can also produce large amounts of immune checkpoints, which is how they evade detection by the immune system.
Immune checkpoint inhibitors block or disable immune checkpoints, which helps the immune system identify and destroy cancerous cells.
In the case of colorectal cancer that tests positive for microsatellite instability (MSI) and changes in mismatch repair (MMR) genes, this means the immune system will attack cells with neoantigens.
When should you consider subcutaneous immunotherapy?
Mentioned above, subcutaneous immunotherapy is becoming a treatment option, and you and your healthcare team might consider subcutaneous therapy for several reasons.
A subcutaneous injection can be administered at a healthcare provider's office, unlike IV infusions, which require a visit to a hospital or an infusion center. This can be helpful if getting to a hospital or infusion center is difficult or time consuming.
Subcutaneous injections also take between 3 and 5 minutes to administer, a much shorter time than IV infusions, which can take between 30 and 90 minutes.
Flexible administration locations and shorter appointment times may make cancer treatment a bit easier and easier to adhere to.
As with any cancer treatment, subcutaneous immunotherapy will be a good treatment option for some people, while other treatment options will be recommended for other people.
If you have questions about treatment options for colorectal cancer, including whether immunotherapy or subcutaneous administration might be treatment options, your healthcare provider will be your best source of information.
