Immune Therapy for Prostate Cancer

Immunotherapy is a form of therapy increasingly used for the treatment of prostate cancer. Also known as biologic therapy, it works by stimulating the body's immune system to better identify and attack cancer cells.

There are seven different types of immunotherapies, two of which are applied to the treatment of prostate cancer. One is a cancer vaccine called Provenge (sipuleucel-T) and the other is an immune checkpoint inhibitor called Keytruda (pembrolizumab).

This article takes a look at the use of immunotherapy in the treatment of prostate cancer, including the indications, benefits, and risks of Provenge and Keytruda in people with advanced prostate cancer.

How Immunotherapy Works for Prostate Cancer

Immunotherapy involves the use of drugs to stimulate a person’s own immune system to recognize and destroy cancer cells more effectively. Certain types of immunotherapy can be used to treat prostate cancer by either:

• Boosting the immune system's natural defenses so that they work harder and smarter to identify and attack cancer cells
• Mimicking components of the immune system to improve how cancer cells are targeted and destroyed

There are currently seven different classes of immunotherapies used for the treatment of cancer. For prostate cancer, drugs have been developed from two of the seven classes.

Cancer Vaccines

Cancer vaccines, also known as therapeutic vaccines, are used to treat rather than prevent diseases. The vaccines stimulate the immune system to produce cells that are "coded" to recognize proteins called cancer antigens, which are found on the surface of cancer cells. By doing so, the immune system can launch a more targeted and robust assault on cancer cells.

The cancer vaccine developed for prostate cancer is called Provenge.

Immune Checkpoint Inhibitors

Immune checkpoint inhibitors are a form of immunotherapy that works by "taking the brakes off" the body's immune response so that it can fight cancer better.

One of the main types of immune cells that help fight cancer is called a T-cell. To differentiate cancer cells from normal cells, T-cells have a protein on them called PD-1 that attaches to a protein on normal cells called PD-L1. The binding of PD-1 and PD-L1 "tags" the normal cells so that they are not harmed during the immune assault.

The problem is that many cancers, including prostate cancer, also have PD-L1 on them. When PD-1 binds to PD-L1 on cancer cells, it hides them from immune detection.

To overcome this, immune checkpoint inhibitors block either PD-1 or PD-L1, allowing the immune system to target and kill the cancer cells more effectively.

The immune checkpoint inhibitor used to treat prostate cancer is called Keytruda. Because it blocks PD-1, Keytruda is also referred to as a PD-1 inhibitor.

Provenge

Provenge is a cancer vaccine approved by the Food and Drug Administration (FDA) in 2010. The drug is used to treat advanced prostate cancer that is no longer being helped by hormone therapy.

Provenge is manufactured in the lab in several steps:

1. First, the person's blood is run through a machine that harvests a type of immune cell called a dendritic cell. The process is known as leukapheresis.
2. The dendritic cells are then exposed to a protein that triggers an immune response specific to prostate cancer.
3. The treated dendritic cells are then returned to the person's body via an intravenous (IV) infusion into a blood vein.

Provenge is given every two weeks for a total of three infusions.

Common Side Effects

Like all drugs, Provenge can cause side effects. Most tend to be mild to moderate and will go away on their own within a few days or weeks.

Some of the more common side effects of Provenge include:

• Headache
• Nausea
• Fatigue
• Joint pain
• Back pain
• Numbness or tingling of the feet or hands
• Fever
• Chills
• Diarrhea
• Constipation

Call your healthcare provider if the symptoms persist, worsen, or become severe.

Limitations and Risks

Provenge is specifically used for people whose prostate cancer has metastasized (spread) and is not responding to hormone therapy. On top of that, the person must be asymptomatic (without symptoms) or only have minimal symptoms.

On rare occasions, Provenge has been known to cause the formation of blood clots that can lead to severe and potentially life-threatening conditions like:

• Stroke, caused by a blood clot in an artery in the brain
• Heart attack, caused by a blood clot in an artery in the heart
• Pulmonary embolism, caused by a blood clot in an artery in the lungs

Some people given Provenge have also been known to experience a potentially deadly, whole-body allergic reaction known as anaphylaxis.

Effectiveness

According to research published by the National Institutes of Health, Provenge may be effective in improving survival times in people with advanced prostate cancer.

Compared to people given a placebo (a "sham" drug used in research), those given Provenge lived slightly longer (25.8 months versus 21.7 months). Some individuals lived for far longer, in some cases up to 41 months.

Keytruda

Keytruda is a PD-1 inhibitor used to treat many different types of cancer, including prostate cancer.

Keytruda was approved by the FDA in 2017 for people with unresectable (unremovable) or metastatic solid-tumor cancers that have progressed despite treatment. Prostate cancer was one such cancer that fit the profile for treatment.

Keytruda is given by intravenous infusion, usually once every three weeks or once every six weeks.

Common Side Effects

Keytruda is known to cause side effects, the most common of which include:

• Fatigue
• Nausea
• Itching
• Muscle aches
• Fever
• Cough
• Loss of appetite
• Stomachache
• Diarrhea
• Constipation

Call your healthcare provider if the symptoms persist, worsen, or are severe.

Limitations and Risks

Keytruda can sometimes cause a severe overreaction of the immune system, triggering inflammation that can affect different organs of the body.

Complications of an infusion reaction include:

• Colitis: inflammation of the colon
• Hepatitis: inflammation of the liver
• Nephritis: inflammation of the kidneys

The risk of an infusion reaction can be lessened by delivering the infusion at a slow rate (generally over 30 minutes or so).

Effectiveness

Some solid-tumor cancers respond better to Keytruda than others. Research has shown that Keytruda may help some people with metastatic prostate cancer but not everyone.

A 2019 study involving 258 people with metastatic prostate cancer reported that Keytruda either stabilized or led to a small reduction in the tumor size. Survival times could vary, but some people treated with Keytruda lived up to 14.1 months. That is roughly double the survival time reported in untreated people.

Based on the findings, the researchers concluded that Keytruda could benefit a small proportion of people with advanced prostate cancer. Those who did benefit saw their cancer slowed for a considerable period of time.

Summary

Immunotherapy involves the use of drugs that stimulate the immune system to better identify and attack cancer cells. Immunotherapies have been developed in recent years to help people with metastatic prostate cancer live longer when other treatment options have been exhausted.

One immunotherapy used in the treatment of prostate cancer is a cancer vaccine called Provenge. It is made by harvesting immune cells from a person's blood and exposing them to substances that stimulate a more robust and targeted immune assault on prostate cancer cells.

Another is an immune checkpoint inhibitor called Keytruda, Checkpoint inhibitors work by blocking proteins that shield cancer cells from immune detection. Keytruda is used to treat a wide variety of cancers, including prostate cancer.

Both Provenge and Keytruda are given by intravenous infusion into a blood vein.

A Word From Verywell

The science of immunotherapy is rapidly advancing with new treatments offering hope to people with advanced cancers, including prostate cancer.

This includes an immunotherapy drug called Yervoy (ipilimumab), which is currently approved for the treatment of melanoma and has shown promise in people with prostate cancer.

If diagnosed with metastatic prostate cancer, speak with your cancer team about immunotherapies that may be available to you. Clinical trials are another option and may provide you access to experimental immunotherapy drugs.