Cancer vaccines are one type of cancer immunotherapy, which uses the body's immune system against the disease. Cancer vaccines come in two types: therapeutic, which are aimed at treating an existing cancer, and prophylactic, which are designed to prevent disease.
Prophylactic or preventive vaccines typically target a virus that is known to lead to cancer. Currently, the FDA has approved a vaccine for hepatitis B, which is a known risk factor for liver cancer, and for human papilloma virus, which is a risk factor for cervical cancer.
Although no treatment vaccines are approved, there are many in research trials. Treatment vaccines attempt to strengthen the body's natural immune defenses against cancers already present. The immune system needs this help; it generally doesn't consider cancer cells as foreign and therefore harmful.
The FDA recently rejected a treatment vaccine known as Provenge to treat prostate cancer. Although they rejected the vaccine in 2007, by 2008 patient advocacy groups were still staging protests and waging court battles to get the FDA to reverse course and approve the vaccine. Dendreon, the company sponsoring the vaccine, had presented clinical data that suggested a benefit of slowed tumor growth among treated patients. However, researchers could not prove the difference was not just chance.
Boosting the immune system takes several forms. Some techniques involve altering the amino acid sequence of an antigen, while others might involve putting a gene for an antigen or an immune system-boosting molecule into a viral vector to deliver it to a tumor. Some vaccines alert the immune system's T cells to help them recognize a cancer.
Cancer vaccines can be for specific cancers, such as melanoma or prostate, or they can be more generic, "one size fits all." Tumor cell vaccines are the most common, and use cancer cells either from the patient or from one or more other patients' cells grown in the laboratory. Tumor cell vaccines use killed cells removed during surgery. Cells are injected into the patient to rouse an immune response.
Early Discovery and Research
The notion of a cancer vaccine has been around for more than a century. In 1893, William B. Coley of Memorial Hospital in New York developed a primitive "vaccine." The scientific basis for immunotherapy for cancer dates back some 50 years. In the 1950s, Richmond Prehn, while at the National Cancer Institute, demonstrated that mice could be immunized against chemically induced tumors.
In the early 1970s, researchers began testing early generation melanoma vaccines. By the 1980s, researchers at the National Cancer Institute showed that interleukin-2 could be used to treat tumors in patients with melanoma and renal cancer and that treating these tumors with antibodies was an effective therapy.
Latest Research Directions
Today, researchers are capitalizing on newfound knowledge gained over the last decade of how the immune system works.
In 2008, researchers presented new data on the GVAX vaccine and found that when combined with the chemotherapy ipilimubab it could lower prostate specific antigen levels in some patients. High PSA levels are a known marker for prostate cancer. Treatment with the combination reduced PSA levels by more than 50 percent in five out of six patients.
Researchers also tested a live Listeria vaccine as a possible therapy for cervical cancer. Among 15 women with progressive, recurrent or advanced cervical cancer, three had tumor reductions of approximately 20 percent. Seven other patients had stable disease. One patient was completely tumor free.
Building on past experience, researchers are also learning that treatment with a vaccine can boost the immune system in such a way that patients will respond better to more conventional therapies. For example, in non-small cell lung cancer, L-BLP25, a peptide vaccine, showed increased survival at 30.6 months compared with 13.3 months without the vaccine, among patients who had responded to chemoradioatherapy. In lung cancer animal models, dendritic T cell vaccine increased the efficacy of paclitaxel.