Shark cartilage, despite a long subculture of belief, has no effect against cancer. A new study presented at the annual meeting of the American Society for Clinical Oncology showed no effect of shark cartilage on non-small cell lung cancer.  Previous well-designed studies have also shown no benefit from shark cartilage.  If only this were real medicine (and not “alternative”) the story would be all-but over. Unfortunately shark cartilage as a cancer treatment is going the way of laetrile – immune to evidence, propped up by true believers and conspiracy theories.

The notion that shark cartilage might be an effective cancer treatment apparently stemmed from the observation that sharks (who do not have bones but whose skeletons are composed almost entirely of cartilage) do not get cancer. This dubious observation was followed by the even more dubious logic that it must be their cartilage that has magical anti-cancer properties. A liberal dose of wishful thinking, biased observation, and exploitive marketing then led to the belief that consuming shark cartilage could treat or cure cancer in humans.

In fact, sharks do get cancer.

But it’s too late, the belief is out there. The need for hope at all costs and the relative absence of critical thinking skills has proven most effective in sustaining beliefs, even when the core claims have been utterly shattered. Such is human nature, and the need for science and the nurturing of the critical thinking that does not seem to come naturally to our species.

The real tragedy is that our scientific and healthcare institutions have become distorted and compromised by social forces of ignorance and irrationality coming in the guise of openness, freedom, and multiculturalism. These institutions should be serving and protecting society by following a mature and thoughtful system of ethics and scientific methods. They should be rocks that can weather the storms of fads and fashionable nonsense. Instead they are now largely promoting them by offering an undeserved imprimatur of scientific legitimacy.

The shark cartilage story is a good example. The idea has no a-priori scientific merit, and lacked any empirical support. That should have been enough, but this was complicated by popular belief. Of course, popular belief was being driven largely by con-artists selling shark cartilage as a cancer cure suppressed by the evil cancer-treating industrial complex.

Now I admit I have mixed feeling about doing research on questionable but popular CAM treatments. I certainly benefit from having good scientific data to back up my skepticism about such treatments. I can now confidently say to patients who ask that shark cartilage as a cancer treatment has been studied and adequately demonstrated not to work. I also agree with taking popularity into consideration in deciding what to research.

However, the flip side is that hundreds of cancer patients were subjected to this experimental treatment when the prior probability of any benefit was negligible. (They also received standard treatment – not to give it would have been blatantly unethical.) These were cancer patients who were willing to participate in clinical research – a limited resource. So resources of time, effort, appropriate subjects, and money were diverted from more promising cancer research in order to deal with a popular but worthless treatment. This is an inefficiency in biomedical research that we would all be better off without.

Moreover, the negative results of this and other studies is unlikely to eliminate the use of shark cartilage as an alternative cancer treatment. Within mainstream medicine, these studies would appropriately end the use of a potential new treatment.

One other side note – there are a few studies looking into the fact that shark cartilage contains certain substances that have angiogenesis inhibiting effects (they inhibit the formation of new blood vessels). This has lead some to speculate that shark cartilage may block the formation of blood vessels to cancerous tumors and work its effect that way. I find this totally unconvincing, however.

If you take any complex biological product – plant or animal – and then look at all the chemicals and substances that constitute it, you are likely to find something that has some biological effect that you can then speculate might lead to the clinical effect that is being claimed for the product. This kind of in-vitro basic science research is interesting within the context of legitimate science, but in the context of controversial treatments it often becomes a hunt for post-hoc rationalization – almost a data-mining exercise. This most commonly takes the form of showing that there is some effect on cells of the immune system, leading to the claim that the product “boosts the immune system” and from this the final clinical effect is extrapolated.

What this highlights is the difficulty of extrapolating from basic science research to ultimate clinical effects. Always be suspicious of clinical claims of benefit based solely on Petri-dish evidence. Most of this type of information does not pan out as we expect. Second, the fact that someone can find a putative mechanism for an alleged clinical effect does not, in and of itself, provide much support for the clinical claim. Biology is so complex that it is probable something will be found that can be loosely tied to the clinical effect.

The bottom line is that clinical claims must be plausible and must also be supported by solid clinical research. Also, science works by connecting all the dots very carefully. If we are going to make a connection between a cellular effect seen in a test tube and a clinical effect, we have to do the dozens of studies necessary to carefully make a connection between the two and eliminate all other interpretations.

What I see in the CAM world is a parody of real biomedical research, but all the real key steps are missing. It is the very definition of pseudoscience. And the marketing of shark cartilage for cancer is just one example.

But now we have yet another opportunity for the CAM community to show that their research is more than just a propaganda tool. If it is, then the promotion of shark cartilage as a cancer treatment should vanish.