How does subcutaneous cancer immunotherapy work?

The body's immune system has natural defenses against cancerous cells. When mutations, errors, or damage to a cell’s DNA create abnormal cells, the immune system will destroy these cells, breaking them down and removing the pieces from the body.

However, cancers still occur. Cancerous cells may contain proteins that allow them to hide from and evade the immune system. Some cancers suppress immune system function, weakening the immune system and its response. Other cancers grow too quickly for the immune system to keep up.

Immunotherapy is a type of cancer treatment that helps the body's immune system fight cancer. There are many different immunotherapy drugs available, and different drugs can be administered in different ways. Most are given as intravenous (IV) infusions, some are taken as pills, and some are now given as subcutaneous injections.

Here, we look at subcutaneous immunotherapy and how it works.

What is the subcutaneous layer?

The subcutaneous layer is a layer of fatty tissue just under the skin. A subcutaneous injection is delivered into this layer of tissue with a needle. An injection is typically administered in the abdomen or thigh, though specific drugs can only be injected at specific sites.

Once a drug is injected into the subcutaneous layer, it will be absorbed into the body. More specifically, the drug will be absorbed into the lymphatic system. The lymphatic system is the body’s network of lymph nodes and lymph vessels, which transport immune cells throughout the body. Because the lymphatic system connects to all parts of the body, the drug will be able to reach cancer cells throughout the body.

Are subcutaneous injections as effective as IV?

Like any cancer treatment, subcutaneous immunotherapies are extensively studied and tested before they are approved. Studies show that subcutaneous immunotherapy drugs are as effective as intravenous infusions of a drug.

However, it’s important to keep in mind that different treatments work for different people. While one immunotherapy drug may work well for many people, others will respond better to other therapies. Cancer is different for everyone, and everyone with cancer will need to work with a healthcare team to determine the most effective approach.

Why might a healthcare provider recommend subcutaneous immunotherapy?

Subcutaneous injections may be more accessible for some people. Compared with intravenous infusions, subcutaneous injections require shorter appointment times and less travel.

An injection typically takes between 3 and 7 minutes, while a typical infusion of immunotherapy takes between 30 and 60 minutes. Injections can also be administered at a healthcare provider’s office. This means a person will not need to visit an infusion center or a hospital to receive this treatment.

Some studies have found that subcutaneous immunotherapy may be associated with a lower risk of serious side effects compared with immunotherapy drugs administered intravenously.

Why might a healthcare provider not recommend subcutaneous immunotherapy?

Receiving a subcutaneous injection requires enough subcutaneous tissue. People who are significantly underweight may not have enough subcutaneous tissue to receive an injection.

Subcutaneous immunotherapy is also a new and emerging treatment. While several drugs are available (and more are under development), your healthcare provider may recommend a drug (or a combination of drugs) that is not available as a subcutaneous injection.

If you have questions about immunotherapy—or any other aspect of treatment—your healthcare provider will be your best source of information.