Treating and Preventing Cancer with Vaccines (Page 5 of 5)

Present and Future of Cancer Vaccines

In studies conducted in laboratory animals, cancer vaccines that stimulate the immune system have caused cancers to recede. In humans, however, the situation is more complicated. As discussed in Cancer Vaccine Strategies, cancers have developed ways of evading the immune system. Researchers now have a better understanding of how cancer cells avoid detection by the immune system, and they have developed new strategies for stimulating a more powerful anticancer immune response.

Therapeutic cancer vaccines have shown promise in early-stage clinical trials against several types of cancer, for example:

-In one early-stage study, 18 of 20 patients who were vaccinated against non-Hodgkin's lymphoma stayed in remission for an average of four years. The vaccine used in this study contained a protein specific to each patient's tumor cells (that is, each patient was given an autologous vaccine) as well as two other substances to help boost the immune response.

-In a phase I/II study, three of 33 patients with advanced non-small cell lung cancer had a complete remission of disease and were still alive at least three years after vaccine therapy. To make the vaccine, researchers added the gene for the cytokine granulocyte–macrophage colony stimulating factor (GM-CSF) to each patient's tumor cells - that is, each patient was given an autologous vaccine.

-Another early-stage trial showed that, when administered along with a melanoma peptide vaccine, an antibody that blocks the activity of a key immune-system regulatory molecule caused tumors to shrink in patients with metastatic melanoma.

It is important to note that the promise of early-stage clinical trials, which usually enroll only a small number of patients, is not always sustained in larger trials. Early studies of another melanoma vaccine suggested that the vaccine might help prevent melanoma from coming back in patients who were at high risk for recurrence. However, in a subsequent large trial that included 774 patients who were at high risk for melanoma recurrence, high-dose interferon proved superior to the vaccine in preventing melanoma from coming back.

Researchers still have a lot of work to do to demonstrate clearly that cancer treatment vaccines can be effective. It is possible that vaccines will prove more effective when combined with other therapies and that multiple vaccinations may be necessary for a benefit to be seen.

Ongoing trials seek to find the most promising situations for the use of cancer vaccines and the best approaches for making such vaccines work. Only when rigorous trials provide evidence that a particular cancer vaccine is both safe and effective against a specific type of cancer will the FDA consider approving that vaccine as standard treatment.

_{This article was reproduced from the web site of the National Cancer Institute.}