Related Pages What Is a Clinical Trial? A basic description of the reason for, and the kinds of, clinical trials. Cancer Vaccines Cancer vaccines are intended either to treat existing cancers (therapeutic vaccines) or to prevent the development of cancer (prophylactic vaccines). Fact Sheet 7.56

Only you can make decisions about what treatment you should have. You should always discuss any treatment option thoroughly with your doctor and possibly your loved ones. The following questions and answers may help you to think about whether taking part in a cancer vaccine trial might be an appropriate option for you.

Is a standard treatment available for my cancer?

If a standard treatment exists for your cancer, you should not choose an experimental vaccine therapy over the standard treatment. The FDA has not yet approved any cancer vaccine for use as a standard treatment. A vaccine may be an appropriate addition to standard therapy but not a replacement for it. Currently, many therapeutic cancer vaccines are being used after the patient finishes standard treatment.

Some cancer vaccine trials test a standard treatment with or without the vaccine. A few test the standard therapy against the vaccine. Some cancer vaccine trials test the cancer vaccine against a placebo vaccine or test the cancer vaccine in combination with various adjuvants. In these cases, the patient has already received standard therapy.

Is the main goal of treatment to prevent my cancer from coming back or to shrink existing tumors?

In studies using laboratory animals, cancer vaccines show the most promise at preventing cancer from coming back after the primary tumor has been eliminated by surgery, radiation, or chemotherapy. When the immune system has to detect and fight a smaller number of cancer cells, it is more likely to be successful. In contrast, shrinking existing tumors using vaccine therapy is more difficult. When the immune system is matched against a large number of cancer cells, it is more likely to be overwhelmed and ineffective—an out-numbered army.

It may be appropriate to consider experimental cancer vaccines for advanced cancers once all other therapies have been exhausted, when standard therapy is no longer effective, or in combination with other therapies. For example, in some patients with melanoma and renal cell cancers, treatment with the cytokine called interleukin-2 (IL-2) has caused large tumors to shrink. Many current cancer vaccine clinical trials are testing vaccines in combination with other therapies such as IL-2. It is also possible that newer and more potent vaccine strategies could cause advanced cancers to shrink.

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