Colon cancer screening and detection is vitally important. When detected early, colon cancer is nearly always curable. Unfortunately, by the time a person has symptoms of colon cancer and seeks medical help, the cancer often has spread beyond the colon, making cure much more difficult to achieve.
To solve this problem, health experts recommend regular colon cancer screening. It seems that this would be a no brainer. If everyone were screened, far fewer people would die of colon cancer. The only problem is that many people skip screening, because they are afraid that a colonoscopy is too invasive or embarrassing.
Can Fido Find Cancer?
A new report in the medical journal Gut has demonstrated a non-invasive approach for colon cancer screening and a specially-trained, female black Labrador retriever is leading the way. A specially trained dog, or even a "sniffer machine" that could detect cancer-related odors (chemicals) in a stool sample would be invaluable. Having a non-invasive way to find cancer early would likely increase the number of people willing to get life-saving colon cancer screening.
For this study, 37 stool samples were collected from patients known to have colon cancer. One-hundred forty-eight samples were collected from cancer-free study volunteers. The cancer-sniffing dog performed as accurately, or more accurately than many current colon cancer screening tests.
- The sensitivity of dog scent detection of stool samples was 97%. Sensitivity is the ability of a test to correctly identify those with a disease, as having the disease.
- The specificity of dog scent detection of stool samples was 99%. Specificity is the ability of a test to correctly identify people without the disease as not having the disease.
To put this another way, the dog only mistakenly identified 3% of the samples as having cancer in people who didn't actually have cancer. These are what we call "false positives." The dog only missed 1% of cancer in people who actually did have the disease. This is what we call a "false negative."
Dog Comparable to Colonoscopy
Even colonoscopy, which is considered the gold standard for colon cancer detection has a sensitivity of 94%. This means colonoscopy mistakenly identifies 6% of people as having cancer when they don't.
Colonoscopy has a specificity of 100%. This means it doesn't ever miss colon cancers if they are present in the colon where the scope reaches. So the trained cancer-sniffer dog came within 1% of the gold standard test for false negative test results.
Even more promising is that the dog was especially good at detecting early stage colon cancers, which are the ones that don't often give symptoms.
The Future of Colon Cancer Odor Detection
This study is a proof of concept - that a specially trained dog can be used to detect colon cancer. It's a little early to take the dog colon cancer-sniffing test to prime time. More studies are needed, and more dogs would need to be trained too.
But even beyond the dog herself, this study shows that stool samples from people with colon cancer must give off some particular odor that signals the presence of cancer. If this "cancer substance" (or substances) can be identified, a cancer-sniffer machine could be designed to find it too. This opens up a whole new angle for finding, and curing, early stage colon cancer.
