Why Don’t We Have Cancer-Sniffing Dogs?

Why Don’t We Have Cancer-Sniffing Dogs?

{♫Intro♫} Right now, as we speak, there exists a relatively
inexpensive method for detecting certain early cancers with an accuracy rate of up to ninety-seven
percent. You might even have one in your room with
you right now home. And it probably goes wild when you reach for
a tennis ball or the doorbell rings. Yes — we’re talking about the domestic
dog. So why aren’t there domestic dogs trained
to detect cancer in every hospital on the planet? It’s complicated. Anecdotally, there are a lot of stories out
there about dogs who seemed to smell lung cancer on their owner’s breath, or became
unusually interested in a particular mole later found to be cancerous. But there’s also more rigorous evidence
too. In fact, a 2019 study found that some dogs
can detect lung cancer in blood samples with almost 97% accuracy. And that’s not too surprising when you consider
that dogs can learn a huge amount about other dog’s health, age, and reproductive status
by smelling their butts. But how they’re able to separate the smell
of healthy cells from cancerous cells is pretty remarkable. Cancer cells produce odiferous chemicals called
volatile organic compounds, or VOCs. And dogs sometimes actually detect a particular cancer’s
signature blend. The particular group of VOCs produced by a
given type of cancer can act as a biomarker for that cancer. A biomarker is any biological characteristic
that can be measured and then used to identify some sort of process in the body. If that sounds vague, it’s because biomarkers
can be a huge range of things. But in this case, they make it possible to tell healthy
tissue from cancerous cells. VOCs are produced during normal biological
processes. They might be present in skin, urine, blood, sweat, stool, or even a person’s
breath, where they can serve as biomarkers for both healthy and diseased biological processes. That’s because the VOC profile you see in
these places is different in people with, say, lung cancer, than it is for healthy people. And it’s different in people with lung cancer
than it is in people with ovarian cancer, or bladder cancer, or breast cancer. Detecting cancer-specific VOCs is complicated
for us humans because there are so many to sort through — there can be as many as 3000
different VOCs in a person’s healthy exhaled breath. In 2003, researchers were able to identify
two classes of VOCs — alkanes and monomethylated alkanes — as possible tumor markers in lung
cancer patients. The specific biomarkers of many other cancers
haven’t been identified yet. That’s mostly because it’s challenging
to pick out the few VOCs that are specific to a given cancer from all the other given
compounds that might be present in a sample. But if that two 2019 study is any indication,
some of our fine furry friends can be trained to sniff them out. So you’d think every hospital and doctor’s
office and diagnostic lab that doesn’t already have a cancer-sniffing dog would be trying
to get one. But there are some technical barriers, despite these pooches’ impressive accuracy. Dogs thrive in jobs that require a close relationship
with a handler. Dogs that sniff out drugs or bombs, or who
look for survivors of disasters, work in a very engaging environment. These jobs are exciting for dogs. The animals
are working in an environment with a lot of external stimuli, and that moment where a
survivor is found under a pile of rubble can be, like, emotional for everyone involved. And a search and rescue dog’s handlers can
confirm that the dog has found its target, which means the dog will always get the right
reinforcement at the right time. Compare that to a bunch of dogs in a lab sniffing
out sample after sample, most of which probably won’t be positive. That could be frustrating for a dog. But the biggest problem in that real-life
scenario is that the handlers can’t give the dogs any feedback if they don’t know
which samples are cancerous. If they reward the dog for every alert, they
could unknowingly be rewarding false positives, which will ultimately impact the dog’s accuracy. No rewarding means no joy, and those cancer-sniffing
canines could easily start regretting their career choice. And even though the dogs can be pretty accurate
in theory, things could be different in practice.. Like people, dogs are fallible. I don’t wanna… don’t send me hate mail! And unlike a hypothetical cancer-sniffing
machine, a dog might work better in the morning and not so great in the afternoon, which would
result in different rates of accuracy. You don’t have that kind of problem with a
machine, which operates the same way every time you use it. Finally, it’s a huge investment of both
time and money to train a cancer-sniffing dog. A single dog needs to spend six to eight months
sniffing a minimum of 300 biological samples before they can be a certified cancer-sniffer. But that doesn’t mean we can’t learn a
lot from cancer-sniffing canines. Dogs can still help us identify the odor signatures
of different cancers. We could use that information to build electronic
noses — a robot cancer-sniffing dog. Like, not literally, but it was fun to say…. These devices are already being tested, but
more work needs to be done to determine which VOCs the noses should be looking for, as well
as to improve their overall accuracy. So far, some studies are using electronic
noses to look at patterns of VOCs, rather than picking out specific ones, because the
specific VOCs aren’t always known. And electronic noses still aren’t as accurate
as some dogs are. Other medical conditions, for example, can
sometimes interfere with the machine’s ability to spot cancer. One study on using VOCs to detect bladder
cancer found that the presence of an infection could reduce the accuracy of the electronic
nose. Which means there’s more progress to be made. Still, while it’s fun to imagine legions
of lab coat-wearing canines quietly saving lives behind the scenes, it’s probably not
going to happen in quite that way. But the things we’ve learned from dogs and
their amazing olfactory abilities are already helping us build technologies that will save
lives through early diagnosis. So break out the tennis ball, and thank your
best friend for their help. Thanks for watching this episode of SciShow.
If you like what we do here, you can support us by joining our community of awesome patrons.
Patrons get access to neat perks, like our After Hours podcast. If that sounds interesting
to you, check out patreon.com/scishow. {♫Outro♫}


100 thoughts on “Why Don’t We Have Cancer-Sniffing Dogs?”

  • Please do something on Red light therapy. There are REALLY expensive lights on the market right now and they keep saying "scientifically proven".

  • So let’s hypothetically say we had a machine with say 75% accuracy that could indicate a pre-screening would we use that?
    I think we can get over the handler, behaviour.. there are ways around reward (already in the comments)
    The fundamental problem seems to be that it’s a dog, people (and lawyers) react differently to being told the pre-screening machine suggests you may have a elevated risk and we recommend a course of action (be that serology or MRI or something else) to “the dog thinks you have cancer “ (Alzheimer’s or a whole set of other potential diseases).

    Just my 2c but I think the problem is perception above others

  • Hey, we've all smelled what comes out of a dog's poo-hole which can be potent enough to turn your guts out. They say a dog can smell 10,000 times better than a human, and yet there they are sniffing each other's arseholes like it's flowers. How do they do that!?

  • check out the bomb and tuberculosis sniffing rats in Africa: APOPO. These rats can clear hundreds of sputum samples in a fraction of the time the labs can and often more accurately. Which would negate your argument about machines being more accurate. Dogs (and other animals) giving false positives is more related to training methods – check out differences in correct alert while using positive vs. negative reinforcement training methods.

  • Too many dogs are only interested in sniffing people's crotch. This would result in too many tests for non-existing cancer in private parts.

  • Dogs ability to smell cancer makes sense.

    I work in EMS, in a few years ago we got notified of a possible dog attack.
    When we arrived on scene we found a great Dane holding down a child.

    Come to find out it was not an animal attack.
    The child had a severe seizure disorder. The dog was trained to smell the seizure before it began. Would warned the person that the seizure was about to begin. And then hold down the childhood that they would not hurt themselves until the seizure had passed.

  • As far as I know cancer dignosis is only about 50% accurate as is, a dog that loses accuracy in the afternoon is fine , why not do the tests in the morning?
    I guess there's a business opportunity there for someone to start a clinic employing dogs for non invasive cancer detection.

  • Robot Cancer Sniffing Dogs!!! Good line. I said it in my Arnold Schwarzenegger terminator voice and it sounded a LOT better!!!

  • 3:47 sniffing for bombs is also extraordinary unrewarding, which is why they let them find a planted toy/sample after a while, they can use the same trick for labs

  • 4:54 Domestic dogs will know your history. This may sound crazy, but dogs probably smell 1000 types of cancer on every single healthy "owner" every day, it's only when the levels get above normal that they get extra interested: meaning it's more about that mole that has gone out of control (or gone critical). Even if we develop a chemical way to detect the odors, it's going to be more about "is this a old cancer in your body, or a new one"

  • when you throw a treat on the ground and the dog can't find it right away, but it's so visually obvious and you think "it's right there dummy!" the dog thinks the same thing when you are trying to find the cancer on your skin "it's right there dummy"

  • There is a bias in this channel, widely shared across the Global North, locating Science only in wealthier, "developed" countries. In fact, a MUCH better animal exists for this role, at least as intelligent as a dog, with at least as sensitive a nose (and easier to train) that is already working in a variety of bio-detection roles which requires sensitivity well into the ppb (that's "billion" and maybe better) range. This is the humble rat (see https://www.apopo.org/en). They have moved from being the most reliable and safest landmine detector technology to screening suspected TB samples more accurately and orders of magnitude faster than the most skilled human. Some years ago, I had a hand in setting up Young Scientist Tanzania (based on YS Ireland model) and these animals and their handlers really have to be seen to be believed. Tanzania is a world leader in their training, taking their "Hero Rats" as far afield as Cambodia to clear mines. It's a cultural bias against rats in our world (and, I am convinced how disruptive such animals would be for medical profits, esp in the US) that has discouraged serious research into their use in diagnostics. I love this channel, but I wish it was more focused outside of Europe and North America for their understanding of "science".

  • We need democrats to create a dog union and take 30% of their net pay. Then lobbyist will flood congress and we will have dogs sniffing cancer for 37k a sniff.

  • I think I am a dog. I too need a positive reifrcement after I do something great in my job right away and I get bored of doing the same task over and over.

  • Sieko- Valantin says:

    Before I even watch this vid, my guess is: Because everyone gets cancer. And most times, your body handles it on its own. No need for extra scares.

  • Rose Budeigh-Urmather says:

    My dog had a bark-down at work and bit his manager and now he’s licking his unemployed ass on my couch while I pay for his food rent and toys meanwhile he hasn’t found a job because “he’s got worms right now and it’s not the right time”. I’m done! I want this dog to get a goddamn job again or get the hell outta my house!

  • My little dog began acting really clingy around the time I started feeling the lump. Every night he would lay right next to the spot and that's when I realized that I had cancer. From October 2017-September 2018 it was pure hell and I'm still having to relearn what my body forgot during that year but so far I'm in remission and I hope it stays that way. If it comes back I know I'll die with it…. Cheaper to be buried than to fight it!

  • Michelle Coons says:

    Train the dogs now and then when they smell cancer check that persons voc signatures after many tests this way you could start narrowing down which voc signifies which cancer and then we can build the “robot noses”. But for now I am glad dog diagnostics are not dismissed.

  • Please Complete All Fields says:

    Cancer absolutely has a distinctive smell, in my experience. I've had two cats die of cancer (from the same litter of white cats- predisposed to facial cancers). Towards the end, both had a very distinct smell, and when I searched the topic, theres huge anecdotal support, both with (cancers in) animals ans humans.

    (Its a weird, sickly-sweet, medicinal/chemical smell. Reminded me of hospitals, or cheap disinfectant or something)

  • Surely if your sniffer dog hasn't been rewarded in a while you could bring in someone who you know has cancer for it to 'check' and then reward it for that?
    Presumably in a hospital you can find at least one early stage cancer patient who is willing to be sniffed by a dog?

  • We do have cancer sniffing dogs… they're very VERY expensive though and require vigorous training to detect different types of cancer. My uncle has one and if the dog does a dance on its hind legs next to you, that's the cue that he smells cancer. So far, he can detect lung cancer, breast cancer, certain skin cancers but is still going through training for the others.

  • Stephanie Hight says:

    So a man was in his doctor's office, and the doctor tells him he has cancer. The man requests a second opinion, so the doctor opens the door, a Labrador retriever walks in, sniffs at the man, barks twice and whines to be let out the door. The doctor lets the dog out and says, "Yep, you have cancer." The man objects, so the doctor brings in a cat carrier and lets the cat out. The cat walks around the man, hisses and arches its back. The doctor puts the cat back in the carrier and takes it out of the office. He returns and confirms that the patient has cancer and hands him a bill. The patient looks at the bill and exclaims, "$650!!! An office visit is only $50!" The doctor replies, "Yes, but it's $300 each for the Lab test and the cat scan."

  • Not cancer, but if I'm not sure if leftovers are good or not, I let my dog sniff them out. If he doesn't eat it, it goes in the trash. He has high standards LOL although… He has taken that to mean he must test all food at all times. You know… Got to keep mom safe

  • Strange alternate world: dogs no longer have jobs, become pets. Humans no longer have jobs(automation), become pets?

  • a man of many parts says:

    I hope it's just coincidence, but my dog has started to want to sit between my knees since one leg has started to hurt like it's got a poker rammed up the bones, ankle to hip. On the other hand I've only had him for a month.

  • The HeroRats of the NGO Apopo are trained to do this for tuberculosis and landmines. I see no reason why they can't be trained for this, too.

  • You know this makes since for dogs being able to do this, because diseases can be learned to be avoided, and if you're smell that other dog has cancer then you know that individual will be dying soon. So, you know who can be used as a scape goat, and who resources are not a priority to give to. This also means though that dogs can smell if they themselves have cancer, and if they have been exposed to what that smell means they'll know they'll be dying soon.

  • Another reason dogs might work better than machines is that dogs are smart. They can tell by many different signs if something is wrong with you or other animals.
    I would even go so far as to say, a dog will prevail where a machine won't because there's more to it than just different VOC's. The particular blend of them varies with person to person and the dogs are smart (evolutionary speaking) to tell them apart.

    It's like smelling mint on a banana cake. It doesn't belong there.
    Meanwhile, mint on a chocolate + banana cake is alright.

  • Just find people with and without cancer after having already tested them. Have the dogs sniff. When the dogs get it right reward them. Eventually you can start slipping in un-tested patients. Give the dog a handler and plenty of breaks and exercise. This is cancer, it's worth it!

  • green gecko boy says:

    Hey, Scishow! Have you guys ever thought of redoing the 4 fundamental forces video? It was really interesting to learn, and I think a lot more people here will be able to easily learn it if you redo the series.

  • My dog actually let me know there was something wrong with my ear. She would sniff that ear several times a day & never had before. I went to my Dr & found out I had an ear infection. I didn't have any symptoms, but she clued me in. The people with cancer sniffing dogs should open a clinic & for a fee the dog will sniff ya!

  • Richard Anderson says:

    Interesting information, but specious excuses why we purportedly "don't have cancer-sniffing dogs." Doesn't help this channel's credibility.

  • Brittnee Tillery says:

    Seems simple enough to start training the dogs by using samples from actual cancer patients, perhaps in late stages to increase the VOCs emitted, and then continue intense training such as drug or bomb dogs until the dogs are approximately 2yrs old.

  • I smelled cancer on a girl once, now i kind of regret not telling her years before she died. :/ I have dyspraxia so i react to smells differently. I didn't want my first meeting with her to be hi my name is X and i think u have cancer. She was a very sweet girl.

  • MakeMeThinkAgain says:

    I don't see the difference between not getting rewarded for sniffing cancer and not getting rewarded for finding explosives. The human makes sure they occasionally smell the right thing and are rewarded.

    The real problem is how many different things they could be testing for. You would need a bunch of dogs testing for a bunch of different conditions. You probably need a robot nose plus machine learning to get the information we really want.

  • I know I'm not a dog, but that weird smell I've felt for the past 10 years every few months for a couple days is really getting to me, I need to get tested for cancer, to put my mind at ease if nothing else.

  • Gordon Lawrence says:

    There is at least tentative evidence that just having a dog reduces the risk of cancer by reducing stress and thereby reducing immune suppression from stress.

  • My dog smelled n confirmed I had breast cancer n also confirmed when it was gone. I can’t thank my dog enough. ❤️❤️🐶❤️❤️

  • Wouldn't they just want to put a bunch of dummy tests in to give the canines some positive reinforcement? Just like… Have a collection of known/cultured samples. Cancer biopsies are cultured all the time, might be viable, and keep the dogs sharp.

    Canine rescue workers will become depressed if they keep finding only dead bodies, so sometimes they hide other workers in rubble for the dogs to find so they will keep going. Also, imagine that being your job, to be a service human for a hero dog with depression. I can't imagine a more fulfilling purpose.

  • Kimberly Archer says:

    Dog trainer here! As far as their reinforcement, there's actually a pretty simple solution – plant positives. Random reinforcement actually works great for dogs, it's like a slot machine! From what I can tell, money is actually the biggest barrier. It would take a long time to train the dog and a ton of labor to find and train those dogs. It's definitely doable, just probably not worth it.

  • so there was this time i was eating lunch, and casually watching a scishow video on my lunch break.
    all of a sudden, i find myself pondering the significance of VOCs emmited by a dogs but….
    thanks scishow…

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