What is Immunotherapy/Vaccine Treatment for Prostate Cancer?
Normally, the body’s immune system, including white blood cells, fight disease and infection. These cells, including T-cells, recognize foreign infectious particles, as well as damaged or diseased cells, and destroy them. This process is what allows our body to be exposed to so many germs on a daily basis and, in most cases, not get seriously ill.
What is immunotherapy and how does it help fight prostate cancer?
Cancer cells are not foreign invaders nor healthy cells. They are cells native to our bodies that have mutated. These mutations allow for cancer cells to evade our immune system’s damage and growth checkpoints to create tumors. Cancer cells have the ability to evade the body’s natural immune response system under the disguise of being a normal, native cell. Immunotherapies as they relate to cancer, are treatments that aim to train the natural immune response into identifying and attacking cancerous cells. Examples of cancer immunotherapies include vaccines, cytokines, and checkpoint inhibitors. There is currently one cancer vaccine on the market indicated for prostate cancer, however, many other immunotherapy options, including additional vaccines, are being researched.1,2
Provenge® is the only cancer vaccine approved by the FDA for prostate cancer. Specifically, the vaccine is indicated for use by individuals with metastatic castrate resistant prostate cancer that presents with few to no symptoms. Provenge should generally not be used by any individual receiving chemotherapy or immunosuppressive agents.
Provenge is made on a case-by-case basis and is tailored specifically to the individual receiving the vaccination. This is done by extracting a sample of the individual’s white blood cells approximately three days prior to vaccination. These cells are sent to a special lab where they are exposed to a protein called PAP (prostatic acid phosphatase). These cells are then re-inserted into the body via an intravenous (IV) infusion, to stimulate the immune system to attack cancer cells that carry this protein (PAP). The vaccine is not intended to cure prostate cancer, however, it has been theorized that it could be an additional life-prolonging option for metastatic prostate cancer that isn’t responding to other treatment options.
The vaccine takes about an hour to completely infuse and is administered three times. Each dosage of the vaccine is infused two weeks apart. Infusion reactions are possible during the administration of Provenge, and reactions should be treated immediately. The most common side effects of Provenge include:
- Back or joint pain
Potentially more severe, but less common, side effects such as high blood pressure (hypertension), low blood pressure (hypotension), and breathing problems may occur, however, these typically subside after treatment. Pain, swelling or warmth over affected areas in your arm or leg may be a sign of thrombosis and should be reported to your doctor immediately. These are not all the possible side effects of Provenge. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with Provenge.
Research is currently underway to identify other additional vaccines and to further define the long-term efficacy and side effects of Provenge. Other notable studies surround a newer vaccine called PROSTVAC. PROSTVAC uses a modified virus containing prostate-specific antigen (PSA) in hopes the immune system will respond and target prostate cancer cells with high levels of PSA. While the preliminary survival data was promising for PROSTVAC, recent results have not shown that PROSTVAC improves overall survival compared with placebo for patients with metastatic castration-resistant prostate cancer.3,4,7
Other immunotherapies and current areas of research
Other examples of cancer immunotherapies include checkpoint inhibitors and cytokines. In regard to prostate cancer, most of these treatment options need further study. More research needs to be done in regards to immune checkpoint inhibitors for prostate cancer, with examples of checkpoint inhibitor treatments including Keytruda (pembrolizumab) and Opdivo (nivolumab), which both target the PD-1 checkpoint protein, and Yervoy (ipilimumab) which targets the CTLA-4 checkpoint protein. Keytruda was granted approval for the treatment of certain solid tumors with a specific genetic marker, or certain solid tumors with a high number of genetic mutations, including certain forms of prostate cancer.8
These checkpoint proteins are what keep the body from attacking its own cells. Cancer cells are able to manipulate these checkpoints to avoid being attacked. By targeting these checkpoints, researchers are hoping to stimulate the immune system to attack cancer cells. Research is also underway to determine the efficacy, if any, of using these types of immunotherapies in combination with vaccines.5,6