Related Pages What Is a Clinical Trial? 1 A basic description of the reason for, and the kinds of, clinical trials. Cancer Vaccines 2 A fact sheet about cancer vaccines, which are intended either to treat existing cancers (therapeutic vaccines) or to prevent the development of cancer (prophylactic 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 ³, 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 (see the journal abstract). 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. A large, randomized, phase III trial of this vaccine is now under way. (See Lymphoma Vaccine Enters Large Scale Clinical Trials ⁴.)
• In a phase I/II study (see the journal abstract), 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. (See Researchers Shut Off Immune Cell Inhibition, Causing Tumor Shrinkage and Autoimmunity in Patients With Metastatic Melanoma ⁵.)

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. (See Interferon Superior to a GMK Vaccine in Preventing Melanoma Relapse ⁶.)

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.

Much work also remains to be done to develop vaccines that can reliably prevent cancers associated with infectious agents. Cervical cancer, for example, is almost always caused by infection with HPV. The FDA has approved a vaccine that prevents infections with two types of HPV that cause nearly 70 percent of all cervical cancers. Researchers must develop new vaccines that are able to prevent infections by all HPV types that can cause this disease.

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.

Glossary Terms

A substance that helps make more white blood cells, especially granulocytes, macrophages, and cells that become platelets. It is a cytokine that is a type of hematopoietic (blood-forming) agent. Also called granulocyte-macrophage colony-stimulating factor and sargramostim.

A biological response modifier (a substance that can improve the body's natural response to infections and other diseases). Interferons interfere with the division of cancer cells and can slow tumor growth. There are several types of interferons, including interferon-alpha, -beta, and -gamma. The body normally produces these substances. They are also made in the laboratory to treat cancer and other diseases.

A group of lung cancers that are named for the kinds of cells found in the cancer and how the cells look under a microscope. The three main types of non-small cell lung cancer are squamous cell carcinoma, large cell carcinoma, and adenocarcinoma. Non-small cell lung cancer is the most common kind of lung cancer.