Immunotherapy, also referred to as biologic therapy, consists of a wide range of treatments to train the immune system to target malignancies. In recent years, immunotherapy has made a major impact on the treatment of metastatic cancer of the prostate.
There are two FDA-approved treatment options used in immunotherapy for prostate cancer. One is labeled a vaccine (though used in therapy), the other is an immunomodulator. Research progresses and immunotherapy shows promising signs for treating metastatic prostate cancer.
How does immunotherapy work?
We know that the immune system is your body’s primary defense mechanism protecting the body from pathogens or abnormal cells. It also protects us against cancer cells.
However, sometimes the cancer cells can escape from the immune system and form tumors. Once the tumor develops, it can weaken the immune system.
This happens because, in cases of progressing cancer, anti-cancer immune responses either never develop or are turned off by cancer. The cancer cells dodge the defense of the immune system by deactivating it.
Immunotherapy mobilizes the immune system to fight cancer. The ability of the immune system of our body to kill infectious cells and cancer cells is remarkable.
Immunotherapy hacks the immune system and retrains the immune cells to fight the cancer cells. It takes advantage of a person’s own immune system to help kill cancer cells.
What does immunotherapy do?
- Trains the immune system to recognize and attack specific cancer cells
- Boosts the immune cells to help them eliminate the cancer cells
- Provides the body with an extra mechanism to improve the immune response
Though labeled a vaccine, Sipuleucel-T is used in immunotherapy for prostate cancer. It is used in men with advanced, metastatic, hormone-resistant prostate cancer, who are asymptomatic or have minimal symptoms.
It is a vaccine made up of the patients’ own immune cells, which have been trained to target PAP (prostatic acid phosphatase) protein, which is highly concentrated in prostate cancer cells and approved by research for patients with advanced prostate cancer.
This vaccine spurs the patient’s own immune system to attack and kill prostate cancer cells. This involves the removal of your immune cells (WBCs) from blood, modifying them in a laboratory to fight prostate cancer, and then reinfusing them back into you through the vein (intravenously).
The vaccine is modified for each patient to match his own immune system through the following process:
- The Immuno-oncologist removes white blood cells from the patient’s blood over the course of a few hours with the help of a special machine.
- In the lab, he exposes the white blood cells to a protein from prostate cancer cells called prostatic acid phosphatase. This exposure trains the white blood cells to recognize prostate cancer cells.
- He then intravenously infuses the trained cells back into the patient’s body through an I.V. pump. The infused cells help other immune system cells attack prostate cancer.
- This process is repeated every 2 weeks. Totally, three treatments are given.
Sipuleucel-T may increase survival in patients with metastatic cancer that is castration-resistant and who show few or no symptoms. It does not reduce PSA levels or stop prostate cancer growth. However, it has been shown to prolong life. The ideal candidates for immunotherapy are those with asymptomatic small-volume disease having low PSAs.
It is approved for men with spreading prostate cancer that is resistant to hormone therapy. It is meant for men with little or no pain and is most commonly given before chemotherapy. Sometimes, though it appears to be effective after chemotherapy.
Common side effects of Provenge include headache, fever with chills, tiredness, back and joint pain, and nausea. The patient experiences these side effects during the infusion period and they usually last for about three days and are treatable with acetaminophen.
Pembrolizumab (Keytruda®), an immunomodulator, is a checkpoint inhibitor that targets the PD-1/PD-L1 pathway and is accepted for patients with advanced prostate cancer that have high-frequency microsatellite instability (MSI-H) or high tumor mutation (TMB-H) – It means a tumor that has a lot of instability. Your MSI gives your doctor an idea of how cancer will behave.
Studies indicate that immune checkpoint therapies can be clinically effective in a subset of patients with metastatic prostate cancer,
Pembrolizumab belongs to a class of immunotherapies that block chemical signals that disguise the cancer cells and activate immune cells that kill the tumor.
Keytruda (pembrolizumab) is a cancer immunotherapy drug developed by Merck and was granted approval by the U.S. Food and Drug Administration (FDA) in May 2017 for the treatment of solid tumors with a specific genetic marker, including prostate cancer.
In cases where the patient’s prostate cancer is resistant to hormone therapy, treatment options are limited. Currently, clinical trials are being conducted for use of several immunotherapy options in patients with advanced prostate cancer.
Pembrolizumab is delivered intravenously once every 3 weeks. Many people stay on immunotherapy for up to two years. The most common side effects include fatigue, cough, breathlessness, nausea, itching, and decreased appetite. Serious side effects caused by overactive immune responses are rare and treated by stopping the drug and starting steroid medications to contain the immune reactions.