The highest of stakes

New Scientist - Editorial, 31 March 2007
Gambling on an untested cancer drug is unlikely to do anyone any good

THEY say that a rumor grows at it goes.
So it was when New Scientist broke a story in January about a drug called dichloroacetate, or DCA, that showed promise in animal studies of cancer. Within weeks, blogs and web chatrooms were buzzing with discussions touting DCA as a new cure for human cancer, and in their desperation some people with cancer began to locate DCA for themselves and take it.

The drug may yet live up to its promise as an anti-cancer agent - clinical trials are expected to start soon. It may even spawn an entirely new class of anti-cancer drugs. For now, however, it remains experimental, never yet properly tested in a person with cancer. People who self-administer the drug are taking a very long shot and, unlikely as it may sound, could even make their health worse.

There is often immense interest in new cancer drugs. Cancer is a scary disease, and patients are understandably eager to learn about any substance that might rid them of it. The reaction to DCA has been unprecedented, however.

One cancer specialist New Scientist talked to likened this reaction to excitement over a drug in the early 1970s that appeared to cure leukaemia in mice. A researcher even went so far as to inject himself with the drug on live television to demonstrate its relative safety. Ultimately, though, the drug proved to have no effect in humans.

What has changed since those days is the speed at which people can find information on the web, discuss it and take control of their own treatment by finding unconventional ways to get hold of unapproved drugs. This last action is a dangerous trend. DCA may be relatively safe compared to some anti-cancer agents, but it is still known to have harmful side effects, such as nerve and liver damage. An added danger is that it may cause complications when mixed with other drugs.

There is no doubt that acquiring the drug from non-medical sources is risky, too. People could be poisoned by contaminants, for example. In addition, DCA is acidic and if it is not correctly buffered it could leave people with burns.

Aside from these dangers, we still do not know if DCA will work in humans - and if it does, in which cancers and at what doses. A comparison with other drugs suggests that its chances of being a «wonder drug» are not large. Of the many anti-cancer agents that seem promising in animals and pass initial (phase I) safety trials in humans, only 1 in 20 is ever approved. For those making it through to large phase III trials, which more accurately measure a drug's safety and efficacy, only 1 in 5 makes it to the pharmacy shelves.

So statistically, drugs that are in phase III trials, although still experimental, offer a greater chance of benefit than DCA. For many cancer patients who have exhausted conventional therapies, enrolling in a clinical trial may be the best option.

There is another altruistic reason for doing this. Without clinical trials, the real risks and benefits of drugs cannot be properly assessed. If the self-administering of experimental drugs caught on, the trials system would crumble. That system was designed specifically to prevent the type of widespread harm caused by drugs such as thalidomide.

At present doctors are struggling to recruit patients for clinical trials of anti-cancer drugs. In the US, for example, fewer than 5 per cent of adults with cancer enrol in clinical trials. In the UK, the proportion of patients who join trials rose from 3.5 per cent in 2002 to 14 per cent last year, thanks largely to a drive to let people know that this option is available to them. The charity Cancer Research UK runs a matching service that helps patients find details of trials that might be suitable for them and provides advice on how to enrol.

Inevitably, these trials will not find an answer for everyone. People who feel driven to try DCA out of desperation should remember that the drug is potentialy dangerous and find a cancer specialist who is willing to monitor their health while they take it. To be diagnosed with incurable cancer is a terrible thing. To shorten a life further or cause greater suffering would be worse still.