A Realistic Picture of Cancer Vaccines

What if a local car dealership was advertising the most amazing sale? Something like “Get a BMW for nothing down and as little as $199 a month!” Would you just walk into the dealership, pick out a BMW and sign a contract without looking at the actual terms of the sale? I’m guessing you just scoffed and said “Of course not! That sounds too good to be true there must be a catch. Of course I would want to find out exactly what I am signing!”

But why? After all, isn’t the car salesman an expert at selling cars? Doesn’t he know more about car sales than you? If he’s the expert, why do you need to do any further research?

Well obviously because there can be all kinds of limitations to a deal like this. Maybe the BMW is used, maybe it depends on having a stellar credit score, maybe $199 only applies to the cheapest model on the lot, and on and on. Obviously, the salesman has a vested interest in you saying “yes” to the deal. His livelihood depends on people buying cars from him.

OK, so what if your doctor tells you that you can prevent or fight cancer with a simple vaccine injection. It saves lives, it’s simple, it’s extremely safe and extremely effective. Do you bother reading “the fine print”? Do you read the product insert? Do you objectively evaluate the information, looking not just for the benefits, but also the limitations? Chances are, if you are like most Americans you will probably spend more time reading the fine print on a car sales contract than researching what cancer vaccines (or many other medical procedures) realistically can and can not do for you or your loved ones.

We’re accustomed to thinking of any new technological advancement in medicine as effective and positive- regardless of actual results. And it’s hard not to when you hear the enthusiasm of doctors and the media about the latest high-tech treatment to debut. It’s exciting, it’s promising, it’s hugely beneficial, it’s the future and it will make everyone’s lives better. It’s hard not to want to be a part of that sort of excitement! Especially when it means taking some kind of action against a condition that may make you feel otherwise powerless to do anything about. Even if the results aren’t actually very effective, just doing something- anythingcan take away some of those feelings of powerlessness.

Let’s start with a few basic problems for cancer vaccines in general. First, is that the concept of vaccination is built on the idea that the immune system will attack foreign bodies like bacteria and viruses and that vaccines can introduce weakened versions of these infectious agents and stimulate the production of antibodies that bind to specific, targeted microbes and block their ability to cause infection. And of course, this is based on the idea that we can get the immune system to “remember” all kinds of diseases for a long term immune response- similar to natural immunity acquired from measles, chickenpox, smallpox etc.

Now, the first problem with the idea of a cancer vaccine is that cancer does not work like viruses such as measles, chickenpox and smallpox. (This rarely occurs to people when they think about vaccination.) If you become infected with any of the aforementioned diseases, you gain lifelong immunity if you fully recover- which most otherwise healthy people will. We know that if you develop cancer, you can get it again. Cancer does not imprint on the immune system the same way infectious diseases do.

So aside from the fact that many vaccines for infectious diseases can be very ineffective, we are talking about applying a solution that has been developed for infectious diseases and applying it to a non-infectious disease to which you can not develop natural immunity and assuming that it will work because it is claimed to have worked with infectious diseases to which you can develop lifelong immunity. And while I think some researchers may have an understanding of this, most laypeople don’t seem to understand this basic concept. (And neither the researchers nor the news media certainly haven’t wanted to bring it up either.)

In fact, from the summary of research on a preventative cancer vaccine heading into human trials, comes another problem with cancer vaccines in general. The tumor antigens are variations of self proteins that the body makes and would probably cause profound autoimmune complications if used in a preventive vaccine. Nonetheless, the researchers feel that their research on mice has proven highly successful. The news media and proponents have been loudly optimistic. Yahoo! News quotes a breast cancer surgeon who claims that it is “100% effective in animal models”. (In contrast, the MMR II package insert states that “As for any vaccine, vaccination with M-M-R II may not result in protection in 100% of vaccinees.”) Human trials began late last year. We will have to see what further research shows.

Optimism and enthusiasm can be contagious- but also misleading or even dangerous. A new vaccine designed to treat breast cancer that is in human trials has been deemed completely safe- after being tested on fourteen women.  Now, if you start thinking statistically, you will notice a glaring problem here. There are many side effects that have a 1 in 25, 1 in 50, 1 in 100 or 1 in 1,000 chance of occurring. Take, for example, the MMR II vaccine. If you read through the package insert, you will find that the chances of a life-threatening anaphylactic reaction to the vaccine are about 1 in 1,000. The chances of this kind of side effect showing up in a trial of just fourteen people are extremely small. Curiously, the co-author of the study on the breast cancer treatment vaccine has been quoted as saying that he doesn’t “want to oversell this” while going on to say that despite the vaccine’s very small trial “…we can say confidently that the vaccine was safe”. I’d be interested to see what he would call “overselling”…

At this point there are only two preventative cancer vaccine approved in the United States: Cervarix and Gardasil for prevention of human papillomavirus infection and subsequent cancer. One cancer treatment vaccine has been approved, Provenge, for use in men with metastatic prostate cancer. However, Provenge is not a “silver bullet” against prostate cancer. It is approved only for certain types of cancer and what it actually does is increase survival of these patients by four months.

We’re not talking about a cure here, we’re talking about prolonging a dying person’s life by a few months. The decision about whether to prolong a dying person’s life by a few months is a highly personal one in my opinion and isn’t really the issue here. The point here is understanding what exactly it means to treat cancer with a vaccine and the results that can be expected. And Provenge is a reminder of the caution we need to take with the enthusiasm about breast cancer treatment vaccines. So far the results that have been released for the 14 person mammaglobin A trial claim that the vaccine has halted cancer progression in 50% of the patients in that trial (about 7 people) for a year. How this vaccine will work on more than fourteen people or for longer than a year isn’t known.  Considering that half of the patients in this trial still had cancer progression at a year, the result for many women may still be something similar to Provenge where patients with certain types of breast cancer may be able to survive for a few months longer than they would (on average) with other treatments.

And yet another problem with both cancer vaccines and vaccines in general lies in the issue of adjuvants. Immunologists know that the killed and live bacteria and viruses in vaccines are often not enough to elicit a reaction from the immune system. (For a more detailed discussion of adjuvants, see my post here.) The National Cancer Institute  states: “Antigens and other substances are often not strong enough inducers of the immune response to make effective cancer treatment vaccines. Researchers often add extra ingredients, known as adjuvants, to treatment vaccines. These substances serve to boost immune responses that have been set in motion by exposure to antigens or other means.” So again, though the adjuvants are supposed to help “boost immune response”, your immune system is often not reacting to the actual antigens in the vaccine, but rather to the adjuvants. The big question no one really asks is whether the immune system is actually being “trained” to recognize and fight diseases when it’s responding weakly (if at all) to the disease antigens in a vaccine.

 

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