Understanding Cancer Vaccines

December 2, 2013
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In this podcast, we discuss vaccines and how they may prevent or treat certain types of cancer. We also talk about how cancer vaccines are being tested in clinical trials.

Transcript: 

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You’re listening to a podcast from Cancer.Net. This cancer information website is produced by the American Society of Clinical Oncology, known as ASCO, the world’s leading professional organization for doctors that care for people with cancer.

Today we’ll discuss cancer vaccines, including how they work to prevent or treat certain types of cancer and how they are currently being tested in clinical trials.

A vaccination, generally called a vaccine, is a way to train the immune system to recognize and destroy viruses, bacteria, or other harmful substance. There are two types of cancer vaccines. One type is a prevention vaccine, and the other is a cancer treatment vaccine.

First, let’s talk about prevention vaccines, which are given to a healthy person to prevent a specific type of cancer. Like most vaccines, cancer vaccines must be given before a person is infected with a virus for it to be able to work. Some commonly known prevention vaccines are those given for chicken pox or the flu. Specifically regarding cancer prevention, the U.S. Food and Drug Administration, or FDA, has approved three vaccines.

Two of these vaccines, Gardasil and Cervarix, prevent infection with the human papillomavirus, or HPV. A long-lasting infection with high-risk strains of HPV can cause certain types of cancer, such as cervical, vaginal, vulvar, oral, oropharyngeal and anal cancers.

The third approved vaccine prevents infection with the hepatitis B virus, or HBV.  A long-term infection with HBV can lead to liver cancer. It’s important to talk with your doctor about whether you should be vaccinated against HPV or HBV.

Now let’s talk about treatment vaccines. A treatment vaccine is a type of biologic therapy, also called immunotherapy, which helps boost the body's natural defenses to fight a cancer. A treatment vaccine is given to a person who has already been diagnosed with cancer. A treatment vaccine may prevent cancer from coming back, destroy any remaining cancer cells after other types of treatment, or stop a tumor from growing or spreading.

Next, we’ll talk about how these types of cancer vaccines work.

A treatment vaccine uses the immune system's natural ability to recognize and destroy antigens on the surface of cells that are harmful to the body. Antigens are specialized proteins found on the surface of cells, including cancer cells, that are not normally part of the body. A healthy immune system can identify, attack and destroy possibly harmful substances by identifying the antigens on the surface of these cells, even remembering the antigen so it can respond again in the future. Because of the body’s natural response to antigens, a cancer vaccine directs the immune system to identify and attack the cancer based on the antigens on the surface of the cancer cells. Most cancer vaccines also contain adjuvants, which are substances that may help improve the immune response.

Most cancer treatment vaccines are still being researched and are only available through a clinical trial, which is a research study involving volunteers.

But, in 2010, the FDA approved sipuleucel-T, or Provenge, for men with prostate cancer that has spread from the prostate to other parts of the body. Sipuleucel-T is a vaccine that’s customized for each patient because the antigens are specific to the patient’s tumor. In this process, the doctor removes some of a patient’s white blood cells, which are the cells found in the blood that help fight infection. Then, these cells are modified in a laboratory and infused back into the patient through a vein. It’s similar to a blood transfusion and it’s intended to teach the immune system to find and destroy prostate cancer cells.

Developing successful cancer treatment vaccines can be difficult for several reasons.

First, cancer cells slow down the immune system, which lets the cancer grow and develop in the first place. As explained earlier, an adjuvant, or substance that helps improve the immune response, may help. This is why most cancer vaccines also contain an adjuvant.

Second, the immune system may not recognize that the cancer cells are harmful. Cancer cells develop from your body’s healthy cells, so they may not look harmful to your immune system.

Also, large and advanced tumors are hard to destroy with a cancer vaccine alone. So, people who get a cancer treatment vaccine also need other types of treatment.

Finally, the immune system of a person who is older or physically weak may not be strong enough to work with the vaccine to destroy the cancer. Also, some cancer treatments may damage a person’s immune system, limiting the body’s ability to respond to a vaccine.

Some researchers think cancer vaccines will work better in patients with small tumors and early-stage cancers. There are several vaccines now being tested in promising clinical trials, in a variety of types of cancer. This research is very important for learning more about cancer vaccines.

If you are considering a cancer vaccine clinical trial, it’s important to talk with you doctor and the research team about all of your treatment options, the schedule of treatment, and the possible side effects.

For more information on cancer vaccines, talk with your doctor or visit www.cancer.net. Cancer.Net is supported by the Conquer Cancer Foundation, which is working to create a world free from the fear of cancer by funding breakthrough research, sharing knowledge with physicians and patients worldwide, and supporting initiatives to ensure that all people have access to high-quality cancer care. Thank you for listening to this Cancer.Net podcast.

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