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Today, the majority of cancers are detected on the macroscopic level, when the tumor is already composed of millions of cancer cells and the disease is starting to advance into a more mature phase. But what if we could diagnose cancer before it took hold- while it was still only affecting a few localized cells? It would be like putting a fire out while it was still just a few sparks versus after having already caught on and spread to many areas of the house. An international team of researchers, led by ICFO- Institute of Photonic Sciences in Castelldefels, announce the successful development of a "lab-on-a-chip" platform capable of detecting protein cancer markers in the blood using the very latest advances in plasmonics, nano-fabrication, microfluids and surface chemistry. The device is able to detect very low concentrations of protein cancer markers in blood, enabling diagnoses of the disease in its earliest stages. The detection of cancer in its very early stages is seen as key to the successful diagnosis and treatment of this disease.
(Score: 2) by opinionated_science on Friday May 23 2014, @11:22PM
Indeed, the training it the hard part. But more importantly there are false readings too, and they need to be very close to 100% to be of use. Blood glucose and EtOH detectors are very highly rated because they are solid state. Read up on them, it is interesting just how technical it is.
I am not saying an animal is not useful, but as a final diagnostic it has many problems. Anecdotal support being only one of them.
Rememeber, the sense receptors are G-protein coupled receptors (GPCR) and therefore they need to have a specific ligand(s) to trigger them. Dogs have a better sense of smell than humans because their evolution has required them to continue to hunt for food. Mice, in contrast have even more receptors than dogs, as their body mass is small and poisons would kill them quickly. Also , probably for predator evasion....take your pick.
Since there needs to be a receptor to detect a molecule, the connection is not guaranteed. Some humans cannot smell asparagus in urine, say. The molecules that were isolated are S-methyl thiacrylate and S-methyl 3-(methylthio)thispropionate.
The point is the molecules are known. We can now craft an objective test for these compounds.
A mutation in the olfactory gene knocks out the detection. Without the molecule, how do you find the receptor and know your dog smells them?
Find the ones for cancers in aspiration and you are onto a winner. Having a dog make happy noises 90% of the time might help, but only if it leads to the molecular basis being found.
A final point is that cancers are unique living systems. They are genetically heterogeneous, making it difficult to assume they would give off the same molecules.
I would not have written so much but the 2012 article had gaping holes in it. That's the good thing about peer-review publications, at least there is something we can both look at, even if we don't agree...
(Score: 1) by Immerman on Saturday May 24 2014, @02:45PM
As a final diagnostic, certainly. But as a fast and cheap screening procedure to decide whether more invasive screening is called for they would be extremely useful, provided the false-negative rate was sufficiently low. Multi-stage screening is hardly a new concept - plenty of screening tests are used that have embarrassingly high false-positive rates simply because they are far cheaper and less invasive than the more reliable tests. Coming up positive may still mean you probably don't have the disease, but if it reduces the number of people who need to be subjected to the more expensive screening by 80% then it's a net win (or alternately, if it means you can cheaply screen people who would otherwise not be screened at all, thus catching many more victims before the disease becomes difficult to treat.)
Take breast cancer for example (one of the cancers reliably detectable by the new "breathalyzers" entering field trials, and thus presumably a safe bet for being dog-detectable). Mammograms are time-consuming, painful, and actually increase the risk of cancer developing by bombarding the tissue with x-rays on a semi-regular basis. If a woman could instead breathe on a dog to get a preliminary evaluation that could rule her out as "safe" then it's a net win - you only need to give mammograms to those who the dog identifies as at-risk. And even if the false negative rate is moderately high, so long as it's comparable to mammograms (which have an embarrassingly high false-negative rate) it's still a net win for the patients who are spared the discomfort and x-ray bombardment.
As for the mutation, so what? A dog with such a mutation couldn't be trained for screening, so it wouldn't be used. Knowing exactly which molecule it's detecting won't make any difference.
(Score: 2) by opinionated_science on Sunday May 25 2014, @02:14AM
well that is one of the major research problems. What effects to the mutations make? Go look at the 1000 genome project, for example, plenty of non-synonymous mutations (e.g. NTSR1 the neutrotensin 1 receptor has 83 non-synonymous mutations from population of 1000). Some mutation will cause constitutive activy (the receptors gets turned "on" permanently), or will cause a receptor to become less receptive with different salt concentrations.
My point is with the exact molecule, we can produce both positive and negative control tests.
So let's leave it as "it's a nice idea but needs more work". The particular study was deeply flawed. And we always want to know the active molecule...
(Score: 1) by Immerman on Sunday May 25 2014, @04:12AM
I won't argue that with the exact molecule and a cheap mass spectrometer we can do far better than a dogs nose - that's obvious. My point is that we've known for almost a hundred years how to do so *without* knowing any specific molecules, just as we've used dogs for search and rescue without knowing exactly what (combination of) molecules allow them to track a specific individual.
And again I say - mutations don't matter. Obviously a dog carrying a particular "debilitating" mutation may be unable to identify cancer - but we don't care. Such a dog won't be able to pass the identification training course and thus won't be an issue - it doesn't matter if it's because they have a nose-compromising mutation or are just particularly dumb or stubborn - they get weeded out by the training regime. It's not like a mutation is going to suddenly disable an already-certified dog, and even if it somehow did regular re-certification would solve that easily enough (and would be a good idea for several other reasons).