A vaccine for cancer seems almost too good to be true. But recent developments in scientists' understanding of both genetics and the immune system are making cancer vaccines a reality. Vaccines for cancer, including a vaccine designed to treat a type of non-Hodgkin's lymphoma (NHL), are now being studied in national clinical trials.

The NHL vaccine is a type of immunotherapy, meaning that it uses the body's own immune system to treat the cancer. But unlike traditional vaccines for infectious diseases, this vaccine is customized to each patient using molecules from an individual patients' tumor. By including this part of the cancer cell in a vaccine, it's thought that the body will be tricked into thinking that the molecule is a foreign substance, and will then learn to attack cancer cells containing this molecule.

Below, Ronald Levy, MD, chief of the division of oncology at Stanford University Medical Center in California, explains how the vaccine is made and delivered, and how it is being evaluated in clinical trials.

What is non-Hodgkin's lymphoma?
Non-Hodgkin's lymphoma (NHL) is one of cancers of the immune system, so this kind of cancer starts in the lymph nodes, the bone marrow and the spleen. We refer to lymphomas according to the types of cells they come from in the immune system. And so we have both Hodgkin's lymphoma and NHL. And there are two major kinds of NHL: low-grade, or follicular, lymphoma and high-grade lymphoma.

How has NHL been treated in the past?
The traditional treatments for lymphomas are mostly chemotherapy treatments. Chemotherapy works by killing cells that are growing and dividing fast. That's probably why the chemotherapy treatments work better for the faster-growing lymphomas. We also have radiation treatments and combinations of radiotherapy and chemotherapy.

Interestingly, for the slow-growing kind of lymphoma that follicular NHL represents, many of the treatments that we have slow it down, but none of them seem to cure the condition, or make it go away forever and never come back. Whereas with the intermediate- or high-grade lymphomas, many patients are permanently cured with the very same treatments.

What is immunotherapy?
Immunotherapy is using the body's immune system to treat a disease. Up until now, the immunotherapy that we've been using has been based on antibodies. We can make these antibodies and then give the antibodies to the person. These antibodies then find the target and bind to it and eliminate it. This is called "passive immunotherapy."

Or we can use "active immunotherapy" such as a vaccine and re-educate the person's own immune system to start recognizing the cancer and start responding as if it were a foreign invader by making their own antibodies.

How do vaccines for NHL work?
For most kinds of cancer, we don't know what makes them different from normal cells. In the case of lymphomas, there is a unique receptor that they have on their surface that distinguishes them from the normal cells in the body. That's called the idiotype, and that becomes the target of the vaccine.

When we vaccinate someone against polio or the flu, we are trying to get the immune system to respond to make antibodies and T-cells that recognize the foreign invader. So here we're making a vaccine out of each person's lymphoma cell idiotype, which is unique. The vaccine goes in and stimulates all the parts of the immune system that can recognize the vaccine, so that they will attack any cells in the body that have that idiotype on it.

Will the vaccine have a long-term impact?
The immune system has memory. When you get a polio shot, your immune system remembers it, so if you ever get infected by polio years later, the immune system remembers the vaccine and makes a quick immune response against it. That's what we hope is going to happen with the vaccine against cancer: The immune system will keep remembering that it was taught to fight the cancer and it will keep fighting it forever.

How is the vaccine made?
What is needed is a specimen from a person with lymphoma, so we can get the tumor cells. That requires a biopsy. Then they take the specimen and isolate the idiotype. The idiotype is made into the vaccine, and the vaccine is injected into the patient. So the vaccine is custom-made for each person using their own tumor. And it's only usable in that one person.

How is it delivered to the patient?
We don't know the best possible way of giving it, but the way we're doing it in the trial that we're doing now is to give it once a month for seven months. It's delivered by an injection under the skin.

At what stage in the research is the vaccine?
We've been doing this research now for about 15 years, and we have very promising early results. We've tested to see how to do it best and to see whether it's safe. Now we're in a situation where we're trying to prove that it really works. In the trials, we have some people getting the vaccine that's made from their own tumor, and some people getting something that looks and feels like the vaccine but doesn't contain the ingredients from their own tumor. And we're comparing these two groups to each other.

The way we're doing it now is to use the standard treatment (chemotherapy) first. When people get what we call remission, where the tumor is gone temporarily, then we use the vaccine to keep it from coming back. If this is shown to work, then I think the next step will be to try to use it before the chemotherapy and maybe to try to avoid chemotherapy and get the immune system to do the job.