This news story is racing around the world this week: A specially trained dog in Japan correctly detected more than 95 percent of people who had colorectal cancer—even early cancers—just by sniffing breath or stool samples.
Not surprising that the media have jumped on it: It’s a cute story and hopeful. But many reports are missing the real point: Rather than replacing colonoscopies with dog-staffed screening clinics, the real goal is to find lab tests that could detect cancer much earlier.
The Japanese study, published in the peer-reviewed journal Gut, in which a dog detected colorectal cancer in breath as well as stools indicates that cancer chemicals might circulate throughout the body. This nudges basic science another step toward identifying one or more organic chemicals present in cancer that might be detectable by simple lab tests.
The dogs are way ahead of humans: They have 220 million olfactory (smell) receptors, compared to our measly 5 million, so they can sniff out mere molecules of certain substances.