Prostate Cancer: Immunotherapy

Immunotherapy helps your body's immune system to better fight cancer. It is also called biologic therapy. This treatment uses medicines that work with your immune system to attack and kill cancer cells.

Immunotherapy may be used for people with certain types of advanced prostate cancer.

There are two types of immunotherapy used to treat prostate cancer:

• Vaccine therapy
• Immune checkpoint inhibitors

Before treatment starts, you'll meet with a medical oncologist. This is a doctor with special training in treating cancer with medicines. This doctor will discuss your treatment choices with you and explain what to expect with these treatments.

A vaccine is a type of medicine that can help boost the immune system. Vaccines are usually given to help prevent infections. But there is a cancer vaccine called sipuleucel-T that can boost the immune system to help it attack prostate cancer.

Sipuleucel-T is used to treat advanced prostate cancer. It's used when the cancer is no longer responding to hormone therapy but isn't causing many symptoms. This vaccine does not cure prostate cancer. It won't lower PSA levels. But it can help people with prostate cancer to live longer.

This vaccine has to be made specifically for each person who receives it. Immune cells (white blood cells) are taken from the person's blood and sent to a lab. These immune cells are then exposed to a protein (called prostatic acid phosphatase or PAP) that is found on prostate cancer cells. At the same time, they are exposed to a chemical to boost the immune response to PAP. This helps the immune cells recognize and attack prostate cancer cells.

The immune cells are then put back into the person's body as an I.V. (intravenous) infusion. This means the cells are put right into the blood through a vein. Once back in the body, these cells help other immune cells attack the prostate cancer. This treatment is repeated every 2 weeks for a total of 3 doses.

The body uses certain checkpoint proteins on cells to stop the immune system from attacking normal, healthy cells. Cancer cells sometimes use these checkpoints to keep from being attacked by the immune system. Immune checkpoint inhibitors are medicines (monoclonal antibodies) that block specific checkpoints. This helps the immune system recognize and attack the cancer cells.

Immune checkpoint inhibitors can be used in advanced prostate cancer cases, where the cancer:

• Begins to grow again after chemotherapy.
• Can't be treated with surgery.
• Comes back (recurs) after treatment.
• Spreads to other parts of the body (metastasizes).

There are two immune checkpoint inhibitor medicines used for prostate cancer.

• Pembrolizumab. This medicine may be used for people with prostate cancer cells that have any of these gene changes (mutations):
  • Changes in the mismatch repair genes (MMR)
  • Signs of microsatellite instability (MSI) in the tumor
  • A high tumor mutational burden (TMB)
• Dostarlimab. This medicine may be an option for people with advanced prostate cancer that has DNA mismatch repair deficiency (dMMR).

Both of these medicines work by blocking a checkpoint protein called PD-1. PD-1 is found on immune cells called T cells. PD-1 normally helps stop the T cells from attacking healthy, noncancer cells in the body. Blocking this protein helps the immune system kill cancer cells.

These medicines are given by an I.V. (intravenous) infusion into your vein. This is done once every 2 or 3 weeks.

Side effects will depend on the type of immunotherapy treatment you have and the medicine that's used.

The vaccine is made from your cells but can still cause side effects. They often happen around the time of the infusion and go away in a few days. Side effects can include:

• Fatigue.
• Fever.
• Chills.
• Headache.
• Back or joint pain.
• Nausea.
• Problems breathing (rare).
• High blood pressure (rare).

Common side effects of immune checkpoint inhibitors can include:

• Cough.
• Fatigue.
• Nausea.
• Constipation.
• Diarrhea.
• Shortness of breath.
• Skin rash.
• Itching.
• Not feeling hungry.
• Joint pain.

In some cases, using these medicines may allow the immune system to attack other parts of the body. This is not common. But it can cause severe side effects, such as damage to:

• The liver.
• The lungs.
• The intestines.
• The kidneys.
• Glands that make hormones.
• Other organs.

Talk with your doctors about what side effects to look for and when to contact them. Make sure you know what number to call with questions or problems. Is there a different number for evenings, weekends, or holidays?

It may be helpful to keep a diary of your side effects. Write down physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your care team to make a plan to manage the side effects.