To understand cancer vaccines, first we must understand cancer and vaccines a little better, separately.
A cell that has become cancerous is still a human cell, this is why cancer is so hard to treat. Were it somehow to become a foreign pathogen, like bacteria, treating it would be as easy as taking antibiotics. But since it is still a human cell, you can't kill a cancerous cell without killing healthy human cells as well. To that end, because a cancer cell is human, our immune systems don't recognize and attack it the way they do foreign antigens.
Vaccines, as we typically understand them, are preventive; healthy individuals receive a dead or weakened strain of a virus or pathogen in question, allowing the immune system to recognize it and build a response in a safe and effective environment, with little threat to the person's health.
In cancer treatment, some vaccines are preventive in this traditional manner while others are therapeutic, meaning the patient must already have cancer. In either case, they do work in the same way as other vaccines in that they stimulate an immune system response to a certain detectable microbe.
Preventive cancer vaccines
In the US, the FDA has approved three preventive cancer vaccines and one therapeutic cancer vaccine.
- The first preventive cancer vaccine to be developed works against hepatitis B virus (HBV) and has become one of the two dozen or so vaccinations routinely given to children in the first years of life in the US.
- Gardasil and Cervarix are the other two preventive cancer vaccines. These are designed to protect a certain population set against infection by specific types of human papillomavirus (HPV), which is linked to cancers of the cervix, vulva and vagina in women.
Therapeutic cancer vaccines
Therapeutic vaccines could arguably represent the burgeoning field of personalized medicine in its purest form. However, they are extremely expensive and thus far have proven to be only marginally effective.
- Provenge is a therapeutic cancer vaccine treatment recently approved by the FDA for the treatment of advanced, metastatic prostate cancer. Provenge was designed to incite an immune system response to an antigen frequently found on the surface of prostate cancer cells, prostatic acid phosphatase, or PAP.
- BiovaxID is a therapeutic cancer vaccine currently in clinical trials that treats follicular non-Hodgkin's lymphoma. Following a biopsy, doctors use proprietary technology to identify what, on the surface of the cancer cell, makes it different from the healthy human cells in the body. For example, cancerous cells often express certain proteins of molecules on their surfaces that differ from those expressed on healthy cells. A therapeutic vaccine is then developed using these so-called 'self-antigens' to create the vaccine, which is injected into the patient, the idea being that it generates an immune system response to the cell surface antigen.
The future of cancer vaccines
As more and more cancers become closely associated with viruses and other microbes, the field of cancer vaccines should grow in proportion to discovery. Viruses have long been suspected of being the primary causes of many cancers, and indeed several have been identified. Clinical trials are currently underway to test the efficacy of vaccines against many different types of cancer.
Additional reading
For a more detailed explanation, please see the National Cancer Institute's fact sheet on Cancer vaccines.
