Dogs are being trained to detect cancer in people, and it's a game-changer. Their keen sense of smell can pick up on volatile organic compounds (VOCs) that are present in the breath, urine, and skin of people with cancer.
These VOCs are unique to each type of cancer, making it possible for dogs to be trained to detect specific types of cancer. For example, a study found that dogs can detect lung cancer with a 97% accuracy rate.
The use of dogs for cancer detection is not only effective but also non-invasive and inexpensive. Unlike traditional diagnostic methods, which often require expensive equipment and invasive procedures, dogs can provide a quick and easy diagnosis.
Dogs are being trained to detect various types of cancer, including breast, lung, and colon cancer.
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Canine Cancer Detection Methods
Advanced imaging techniques such as MRI and CT scans can help detect canine cancer by providing detailed images of the body's internal structures.
Early detection is key, and regular check-ups with a veterinarian can help identify potential issues before they become serious problems.
Blood tests can also be used to detect certain types of canine cancer, including lymphoma, by measuring the levels of specific proteins in the blood.
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Dogs Can Be Trained to Sniff Out
Dogs can be trained to sniff out cancer, and it's not just a myth. Hippocrates famously sniffed his patients, and researchers have found that dogs can smell maladies such as hypertension and malaria.
The smells of disease come from volatile organic compounds (VOCs) that we excrete in our bodily fluids. Scientists first identified cancer VOCs in 1971, but it took until 1989 for someone to put dogs and cancer VOCs together in a report.
A research team in the United Kingdom conducted a study in 2004 to see whether dogs could detect bladder cancer from urine samples. After 7 months of training, the dogs got it right 40% of the time, which was statistically significant.
Positive studies began to accumulate, each inspiring a flurry of media attention and public enthusiasm. But investigators caution that much work remains to be done.
Dogs can identify something that's "cancery" about a sample, rather than specific chemicals. This is why researchers are developing electronic noses with similar capability.
The team used the dogs' diagnoses to train an artificial neural network (ANN) to evaluate the volatile chemicals detected from the urine by GC-MS. The ANN detected cancer samples with high accuracy.
The researchers' eventual goal is to apply their canine-trained machine algorithm to an electronic nose that contains synthetic analogs of animal olfactory receptors.
Methods
The CANDiD study was a prospective sample collection program that enrolled 1,358 client-owned dogs with and without cancer at 41 clinical sites across six countries.
Collection sites included veterinary specialty practices, university/academic veterinary hospitals, and general practices, showing a diverse range of locations where dogs were enrolled.
All subjects were enrolled under protocols that received Institutional Animal Care and Use Committee (IACUC) or site-specific ethics approval, according to each site’s requirements.
Written informed consent was obtained from all owners, ensuring their dogs' participation was voluntary and with their knowledge.
Study Design and Criteria
When designing a study to detect canine cancer, researchers consider several key factors. The study should involve a large sample size of dogs with and without cancer to ensure accurate results.
A control group of healthy dogs is essential to compare with the cancer group. This allows researchers to identify specific biomarkers associated with cancer.
The study should focus on specific types of cancer, such as lymphoma or osteosarcoma, to gather reliable data. Researchers may also consider different breeds, ages, and genders of dogs to account for potential variations.
Blood samples are often collected from participating dogs to analyze for biomarkers. These biomarkers can include specific proteins, genes, or other molecules associated with cancer.
Researchers may also use imaging techniques like MRI or CT scans to visualize tumors and assess their size and location.
Test Performance
Test performance is a crucial aspect of any diagnostic test, and canine cancer detection is no exception. Test sensitivity was defined as the percentage of all cancer-diagnosed dogs who received a positive result.
The test's sensitivity was evaluated by looking at the percentage of cancer-diagnosed dogs who received a Cancer Signal Detected result. Binomial confidence intervals were calculated for this estimate.
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Test specificity, on the other hand, was defined as the percentage of presumably cancer-free dogs who received a negative result. The test's specificity was also evaluated using the testing set.
A subgroup analysis was performed on cancer-diagnosed subjects from the testing set representing a predefined list of three aggressive canine cancers: lymphoma, hemangiosarcoma, and osteosarcoma. This analysis helped to evaluate the test's performance in detecting these specific types of cancer.
The test's performance was also evaluated in a larger subgroup of eight common canine cancers that account for most cancer deaths in the species. These cancers include lymphoma, hemangiosarcoma, osteosarcoma, soft tissue sarcoma, mast cell tumor, mammary gland carcinoma, anal sac adenocarcinoma, and malignant melanoma.
The detection rate for the subgroup of subjects diagnosed with multiple concurrent primary cancers was also determined. This analysis helped to evaluate the test's ability to detect cancer in dogs with multiple types of cancer.
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Subject Information
Canine cancer detection is a growing concern for many dog owners. According to recent statistics, over 1 in 4 dogs will develop some form of cancer in their lifetime.
Some of the most common types of cancer in dogs include lymphoma, melanoma, and mast cell tumors. These types of cancer often have different symptoms and require different treatment approaches.
Early detection is key to improving treatment outcomes and increasing a dog's chances of survival. Regular check-ups with a veterinarian can help identify cancer in its early stages.
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Subject Characteristics
The subjects in the study were mostly dogs, with a mix of purebred and mixed-breed dogs. The training set had 113 purebred dogs representing 40 distinct breeds, and 111 mixed-breed dogs.
There were more females than males in the study, with 117 females in the training set and 413 females in the testing set. The opposite was true for males, with 107 males in the training set and 463 males in the testing set.
The median age of the subjects in the training set was 7.3 years, while in the testing set it was 6.6 years. This difference in age was statistically significant, with the training set representing an older cohort.
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The median weight of the subjects in the training set was 28.4 kg, while in the testing set it was 29.1 kg. This difference was not statistically significant.
Cancer-diagnosed subjects were older than presumably cancer-free subjects, with a median age of 9.7 years compared to 4.2 years in the testing set. This difference was statistically significant and expected due to the preponderance of cancer diagnoses in older dogs.
The majority of cancer-diagnosed subjects had localized or regional disease, with 205 out of 352 subjects falling into this category.
Why Dogs?
Dogs have an incredible sense of smell, with estimates suggesting it's 10,000 to 100,000 times better than ours.
Their anatomy allows them to sniff continuously, separating air into two streams for respiration and smelling.
The section of a dog's brain dedicated to analyzing smells is 40 times larger than that in humans.
It's difficult to wrap your mind around a sense that powerful, but scientists offer a useful analogy: we can see a third of a mile away, while dogs can see 3000 miles away.
Background and Context
People have long suspected that illness has a distinct smell. Hippocrates famously sniffed his patients, and medical investigators have since found that dogs can detect diseases like hypertension and malaria.
Dogs can smell maladies because our bodies produce hundreds of volatile organic compounds (VOCs) through sweat, breath, urine, and other bodily fluids, creating a unique signature smell.
The first recorded identification of cancer VOCs was in 1971.
A dog's keen sense of smell can be a powerful tool in detecting disease, as it can pick up on changes in our odor signature when we're sick.
In 1989, a report in The Lancet detailed the case of a dog that repeatedly sniffed a lesion on its owner's thigh, which turned out to be early-stage melanoma.
A study published in 2004 found that dogs could detect bladder cancer from urine samples 40% of the time after 7 months of training.
This groundbreaking research has since inspired further studies on canine cancer detection, with positive results continuing to accumulate.
Looking Ahead
As we continue to make progress in canine cancer detection, it's exciting to think about the future possibilities.
Researchers are working on developing non-invasive tests that can detect cancer biomarkers in a dog's blood or urine, which could lead to earlier diagnosis and treatment.
Studies have shown that certain breeds, such as Golden Retrievers and Labradors, are at higher risk for developing certain types of cancer, like osteosarcoma and lymphoma.
More research is needed to understand the genetic factors that contribute to cancer development in dogs, but advancements in genomics and epigenomics are helping us better understand the complex relationships between genes and cancer.
Early detection is key, and veterinarians are starting to use advanced imaging techniques like MRI and CT scans to identify tumors and monitor treatment progress.
The future of canine cancer detection looks promising, with new technologies and research methods on the horizon.
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Frequently Asked Questions
What is the best cancer screening for dogs?
For canine cancer screening, a combination of imaging tests such as X-rays, ultrasound, CT scans, and MRI may be used, along with collecting tissue samples for pathology testing. Consult a veterinarian to determine the best diagnostic approach for your dog's specific needs.
Sources
- linkedin (linkedin.com)
- detect (npr.org)
- Medical Detection Dogs (medicaldetectiondogs.org.uk)
- PLOS ONE (doi.org)
- https://doi.org/10.1371/journal.pone.0266623.t002 (doi.org)
- https://doi.org/10.1371/journal.pone.0266623.t003 (doi.org)
- Cancer-Sniffing Dogs: Where Are We Today? (dvm360.com)
- doi.org/10.3389/fonc.2022.1011969 (doi.org)
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