Your immune system is your body’s defense against illness. Immunotherapy is a type of treatment that uses your immune system to fight disease, including cancer. Although it is not appropriate for treating all types of cancer, it can provide great benefit for some.

Here is what you should know about this promising treatment.

1. Immunotherapy helps activate your immune system.

Most approved immunotherapies target the T-cells, or the soldiers of the immune system. Once these cells are activated, they attack and kill cancer tumor cells. Sunandana Chandra, MD, Northwestern Medicine medical oncologist and hematologist at Robert H. Lurie Comprehensive Cancer Center of Northwestern University, explains, “Essentially, we are harnessing a person’s own immune system to fight cancer. The immune system is already supposed to fight it; we are just activating it further.”

This can include one or more of the following tactics:

• Attack or stop the growth of cancer cells.
• Improve or strengthen your immune system.
• Aim to prevent cancer from spreading.

2.  There are several different types of immunotherapy.

Immunotherapy treatment is typically performed intravenously, or directly into the vein. The type of immunotherapy, dosage and length of time will depend on the type of cancer being treated. Some types of immunotherapy include:

• Chimeric antigen receptor (CAR) T-cell therapy, which manipulates your own cells into recognizing cancer.
• Immune checkpoint inhibitor therapy, which blocks proteins that stop the body’s own immune system from killing cancer cells. Most current FDA-approved immunotherapies are monoclonal antibodies, which are proteins designed to target immune cells or the tumor itself, resulting in direct tumor cell death.
• Generalized therapies that help strengthen the immune system without targeting the tumor cell itself.

3. Once your immune system is activated, it continues after treatment is finished.

Another unique thing about immunotherapy is that once the immune system is activated, research has shown that it remains activated. This is because the immune system has been trained to remember cancer cells. This distinguishes it from other cancer treatments, like chemotherapy, which does not have a continued response duration after treatment.

4. Immunotherapy is not appropriate for all types of cancer.

Immunotherapy was first FDA-approved for melanoma, a type of aggressive skin cancer. However, research continues to show promise for treatment in other types of cancer, including certain cases of lung, bladder, ovarian and genitourinary cancers, and classic Hodgkin lymphoma. While it is still perhaps not as widely used as chemotherapy, it is changing the way cancer is treated. Immunotherapy may be a promising alternative for some people who have not had success with other treatment options.

5. There are four main side effects of immunotherapy.

Side effects can vary based on your health before cancer, the type of cancer and the specific therapy treatment you are receiving.

Common side effects include:

• Skin rashes
• Itching
• Diarrhea
• Fatigue

Less common side effects include:

• Muscle aches
• Joint pain
• Changes to your pituitary gland, which helps oversee the function of other glands in your body
• Changes to your thyroid gland, which secretes hormones
• Pancreatitis, or swelling of the pancreas

Dr. Chandra stresses that if you do experience side effects, you should discuss them with your physician right away.

6. Immunotherapy takes time to work.

Immunotherapy trains the immune system to attack the cancer cells, so it may take more time than other types of cancer treatment. Additionally, tumors may swell as they are attacked; this is known as pseudoprogression.

Dr. Chandra explains that clinical visits and imaging are used to assess treatment response. “We’ll usually do scans every three months to see how the tumors are responding,” she explains. She adds that it is important to assess how you are feeling, too. Your care team will monitor you and how you respond to treatment.

7. Scientists are investigating why immunotherapy is successful for some and not for others.

Though immunotherapy has shown promise for some patients, others’ immune systems have not responded to it. “There’s a lot to learn about why some patients respond to immunotherapy, or why some experience significant side effects, whereas some patients may not respond or experience any side effects,” says Dr. Chandra. “Research continues to explore why some patients’ immune systems effectively kill cancer and others don’t respond as well.”