Immunotherapy for Prostate Cancer 

 Key takeaways

• Immunotherapy uses the immune cells of the (organs of the) body to fight tumor cells; in the case of prostate cancer, the prostate gland. 
• Immunotherapy does not treat or cure prostate cancer completely. But, it gives the patients a fighting chance and helps to prolong their life span. 
• Immunotherapy options for prostate cancer include the prostate cancer vaccine and immune checkpoint inhibitors. They have both shown activity against prostate cancer cells, more than other forms of immunotherapy. 

 What is immunotherapy?

Immunotherapy is a type of cancer treatment that uses the body’s immune system to fight cancer cells. The body receives medication that boosts the immune system’s ability to attack the tumor cells as they grow. Immunotherapy can be used singly or in combination with other treatment options to treat Prostate cancer.

 Immunotherapy for prostate cancer

For prostate cancer, immunotherapy as a form of treatment is available to patients. And it's different from other traditional treatment methods such as chemotherapy and radiation. It’s used to manage prostate cancer that has spread to other parts of the body and shows little to no symptoms.

It’s also used when prostate cancer reaches an advanced stage despite low levels of testosterone. Prostate cancer grows best when the testosterone levels are high. But at an advanced stage, some cancer cells grow, even with a low level of testosterone.

In prostate cancer patients, immunotherapy boosts the immune cells of the body. Thus, these cells fight off the tumor cells present in the prostate gland.

The types of immunotherapy available for prostate cancer treatment are:

• The prostate cancer vaccine, and 
• Immune checkpoint inhibitors

 1. Prostate cancer vaccine

There is only one FDA-approved vaccine for prostate cancer: Sipuleucel-T (Provenge). The Food and Drug Administration (FDA) approved it on April 29, 2010.

Like other immunotherapy options, Provenge improves the immune cells’ ability to destroy the tumor cells. It targets prostatic acid phosphatase (PAP), which is a tissue antigen produced by prostate cancer cells. Provenge generates PAP-specific T-cells (white blood cells) that recognize the PAP inside the prostate cancer cells. These T-cells now launch an attack on the PAP. 

The generation of these PAP-specific T-cells happens outside the body, through a process known as leukapheresis. Leukapheresis separates the white blood cells (the body's immune cells) from other blood cells. It then gathers these white blood cells together. 

The healthcare professional carrying out the process exposes the white blood cells to the peptide derived from the PAP, which enhances the white blood cells' ability to fight cancer cells.

The doctor reintroduces these boosted white blood cells into the body. This way, the body's immune system becomes active against the tumor cells.

The preferred way of administering Provenge into the body is via injection into the veins. 

It takes one month to complete the full administration. And it's given in three doses - two weeks apart. 

Because each patient's immune system is unique, Provenge is tailor-made for each individual.

Provenge is most suitable when the cancer is in its advanced stage. Also, for when the patient does not respond to other treatment options.

However, Provenge could still not be the best treatment option for you, even if you meet these criteria. And that's where your doctor comes in to help you determine what's best for you. 

 2. Immune checkpoint inhibitors

Checkpoints are part of the body’s immune system. They prevent immune responses by engaging with the proteins of the immune cells. These proteins of the immune cells are known as T cells. 

Normally, these T cells recognize and bind to particular proteins on the surface of the tumor cells. When they bind, they elicit an immune response, causing the T cells to fight and destroy the tumor cells.

To prevent this immune response, the checkpoints bind to the proteins of the T cells. This binding sends an “off” signal to the T cells. Hence, they can no longer attack and destroy the tumor cells.

Immune checkpoint inhibitors act by binding to the checkpoint proteins. Such that the checkpoints no longer bind to the T cells. This binding prevents the checkpoints from sending the “off” signal to the T cells. So, the T cells are free again and can bind to and attack the proteins of the tumor cells.

 PD-1 inhibitors

Programmed Cell Death 1 (PD-1) is a checkpoint protein found in T cells. Along with the T cells, the PD-1 proteins bind with the proteins of the tumor cells, known as Programmed Cell Death Ligand 1 (PDL-1). The PD-1 proteins prevent the T cells from attacking the tumor cells.

PD-1 inhibitors are drugs that bind to these PD-1 proteins. They free up the T cells to attack the tumor cells. PD-1 inhibitors prevent PD-1 proteins from sending the “off signal” to the T cells.

PD-1 inhibitors include Pembrolizumab {Keytruda), Nivolumab (Opdivo), and Cemiplimab (Libtayo).

Your doctor may administer the medication through intravenous infusion every 2 to 3 weeks for up to 2 years or until the disease progresses.

 Side effects of immunotherapy in prostate cancer treatment

Both the prostate cancer vaccines and the checkpoint inhibitors have some side effects. Since immunotherapy works on the body's immune system, the side effects typically result from an overstimulated or misdirected immune response rather than the direct effects of a chemical or the immunotherapy process.

The side effects you may experience depend on your health status before treatment, the spread of the cancer, the stage of the cancer, and the dose of the treatment. The type of immune checkpoint inhibitor is also a factor. 

The side effects range from mild to moderate to severe. And we'll mention the unique side effects of the two treatment options.

 Side effects of the prostate cancer vaccine

Some of the most common side effects of Provenge include:

• Chills
• Fever
• Nausea
• Fatigue
• Back pain
• Headache
• Joint ache

The Provenge infusion may also lead to more severe complications, such as:

• Chest pain
• Vertigo (dizziness)
• Irregular heartbeats
• Dyspnea (shortness of breath)

These side effects may occur shortly after the doctor administers Provenge into the body.

 Side effects of immune checkpoint inhibitors

Side effects of immune checkpoint inhibitors include:

• Rash
• Itching
• Fatigue 
• Nausea
• diarrhea
• Vomiting 
• Joint pain 

Checkpoint inhibitors may also cause widespread inflammation. And the inflammation can lead to other severe complications. This severity depends on the organ of the body that the affected immune system attacks.

These complications may include:

• changes in skin color and itchiness (skin inflammation) 
• cough and chest pains (lung inflammation)
• diabetes (inflammation of the pancreas) 
• hepatitis (inflammation of the liver)
• hypophysitis (inflammation of the pituitary gland)
• myocarditis (inflammation of the heart muscle)
• nephritis (inflammation of the kidney) and impaired kidney function
• nervous system problems such as muscle weakness, numbness, and trouble breathing.

 Is immunotherapy for prostate cancer a promising treatment?

Yes, clinicians consider immunotherapy for prostate cancer a promising treatment.

Conventional treatment options for prostate cancer, like radiotherapy and hormone therapy, have their limitations. These limitations make them ineffective against advanced stages of prostate cancer. Like hormone therapy that works on the level of androgen (testosterone) in the body. What happens when cancer persists even at low testosterone levels?

As discussed earlier, immunotherapy shows efficacy at the advanced stage of prostate cancer. Once prostate cancer metastasizes, the patient's survival rate drops from 100% to less than 30%. So, there is a need for more effective treatment options.

Since immunotherapy uses the patient's immune system to fight cancer, it opens up new possibilities for prostate cancer treatment. Boosting the immune system makes immunotherapy for prostate cancer look almost natural. No foreign substances are introduced to fight the tumor cells directly.

Also, immunotherapy can be used in combination with other treatment options. This is promising because the patient becomes the center of the treatment plan. And these treatment methods become the tools for achieving the desired treatment goals. 

 Closing

With all these advancements in prostate cancer management, it can only mean one thing for the patient: a sense of hope. Immunotherapy offers a remedy beyond what the more popular cancer treatments, like chemotherapy, offer. 

Provenge and checkpoint inhibitors are promising treatment options for prostate cancer. The possibilities are endless. And a proper consultation with your doctor will help you decide what's best for you or your loved one(s).