What Are Prostate Cancer Vaccines, Will They Be Able To Prevent Prostate Cancer, And Where Can I Find Information About Vaccine Clinical Trials?

Susan F. Slovin, M.D, Memorial Sloan-Kettering Cancer Center

BySusan F. Slovin, M.d, Medical Oncologist, Genitourinary Oncology Service, Memorial Sloan-kettering Cancer Cent
November 19, 2008, 12:19 PM

Jan. 01, 2009 -- Question: What are prostate cancer vaccines, will they be able to prevent prostate cancer, and where can I find information about vaccine clinical trials?

Answer: Vaccines fall in the category of immunotherapy, which implies a wide variety of approaches toward improving the ability of your immune system to recognize the cancer and, obviously, treat it. There is no firm understand as yet as to how cancer starts. We are under the assumption that there is a defect in immune surveillance; there is some sort of immunologic flaw; unfortunately, we don't know what it is, and that's the reason why the cancer continues to progress.

Vaccines are always thought of in reference to vaccines against infectious agents, such as bacteria or viruses. The idea behind a vaccine in prostate cancer is to deal with what we call micrometastatic disease, disease, for example, that we can't see, that we know is there as manifested by increasing levels of PSA. We also know that vaccines may be very helpful in patients who have metastatic disease, that is, disease that we can see on a bone or a CAT scan, and implies disease that may be in the lymph nodes or bone.

The issue with prostate cancer vaccines is that there have been several clinical trials that have been ongoing, and, unfortunately, the results are not ready for primetime. The FDA holds a very high bar as to what kind of treatment would be appropriate for prostate cancer. And, as many people know, a recent trial of a drug call Provenge, which is a cellular product vaccine, meaning it uses the patient's own cells, incubates it with a particular molecule to stimulate the cells and then reintroduces it back to the patient. And that's the idea of what they call a cell product-based vaccine. But the FDA had safety concerns, and, unfortunately, the drug is still under development and consideration, and we are awaiting the results of the Phase III trials.

There are several other trials that are continuing to be accrued. We should have the results of those in the next several months. The concerns that are ongoing is that we must show a clinical benefit as well as safety in order for a vaccine to be approved. And that is the reason the FDA holds very high bars, because we want to make sure there is no toxicity associated with the vaccine.

For vaccine information, I always refer patients back to their doctors, who might have the facilities available for them to be able to be aware of what's ongoing, such as the American Society of Clinical Oncology. I also refer patients to the website of ASCO. There is a patient advocacy group here and there is information available about vaccines. There's also PVQ which is the NCI -- or the government-based -- website. There is Cancer Care. There is also the Prostate Cancer Foundation, Prostate Cancer Coalition and a wide variety of organizations that will allow you to be made aware of clinical trials that involve vaccines.

So I ask patients to be very, very indulgent and be patient, because we will have answers going forward. We continue to work in this area; it's one of significant excitement. There's a lot of things that can be done. We're just not ready for primetime as yet.

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