Can dogs really smell cancer?

Dogs have an extremely strong sense of smell but do they have a role to play in advancing medical science? Kat Arney and Chris Smith sniffed out the answer to Destiny's question...

Kat - This is one of my favourite things because I've actually been to visit the medical detection dogs. They have a little centre outside Milton Keynes. And yes, there are chemicals. They call them volatile molecules that are given off by cancers and dogs can detect them. And there's various anecdotal stories about owners who noticed their dog kind of pawing at them or worrying at them, and then they were diagnosed with cancer.

There are also some experiments, lab tests, if you will, that have been done showing that dogs can pick up some of the smells given off by tumours - various different types of cancers. If they're highly trained - we're talking about highly trained sniffer dogs here - they can be trained to reliably sniff out cancers. There's currently a clinical trial going on in the UK looking at big things like prostate and bladder cancer by getting dogs to sniff people's wee.

The thing about the dogs though is that it's all very interesting, but you can't imagine a dog in every surgery up and down the country because these are very highly trained dogs. They're highly trained to certain types of cancers because different cancers will give off different molecules. So, the universal lab test (I just like saying that, better than a CAT scan) is not going to be really practical.

But what could be really useful is if we can work out, what are the molecules that these dogs are smelling? Because, at the moment, it's really hard to tell the difference between aggressive tumours and tumours that aren't growing very fast. If we could work out what are the dogs smelling, and then develop an electronic sensor - kind of an e-nose that could sniff out those molecules - then that is the basis of a much more widely applicable test.

So, I think the dog stuff is really interesting, and they're very, very cute and they work really well, but I think certainly, if we can find out what they're telling us, that could be extremely useful.

Chris - This is sort of the field of metabolomics, isn't it? Scientists are now beginning to detect various diseases not by looking for individual genes, or individual markers in and of themselves related to a disease. They're saying, "Let's measure lots of chemicals all at once in lots of people who have a condition" and what we'll see is that in people who have that condition, there may be some of those chemicals that are changed just very subtly and individually, very small change, but taken as a population of changes, you've actually got a very sensitive test.

When I was in Geneva a couple of weeks ago at a conference run by the drug company Merck where they were bringing research scientists together from across Africa, I met a chap from South Africa who had invented a breath test for TB, and a blood test. The way this works is that when you have TB and you come in to the laboratory and you give samples to try and tell if you've got tuberculosis, it can take a month before you get the diagnosis, which, if you've already had to trek along way from a remote area for a doctor to get the diagnosis, that's a problem. His technique means you take a blood sample, you look at lots of different markers in the blood and he can tell with more than 99.9 per cent sensitivity whether or not a person has got tuberculosis just from a blood sample. And he can do it in 15 minutes!

Kat - Yeah. The idea of breath tests and blood tests for cancers are certainly very exciting. I think it's definitely one to watch over the next couple of years.