Trained Dogs Sniff Out Canine Cancer

Cancer is a major cause of death in companion animals, with estimates suggesting that between one-third and one-half of all dogs will face cancer during their lifetime. Among these diseases, hemangiosarcoma, a malignant cancer of blood vessel cells, is especially severe and has been described as a “silent killer” because it is often not detected until a dog suddenly collapses. At present, there are no diagnostic tools to identify this cancer early, and the prognosis once it is found remains poor.

To investigate a new approach to detection, Cynthia M. Otto of the School of Veterinary Medicine at the University of Pennsylvania and colleagues studied whether hemangiosarcoma produces a distinctive scent pattern that dogs can recognize. Their findings, reported in The Veterinary Journal, focus on volatile organic compounds, the chemicals responsible for smells. According to first author Clara Wilson, “We’re picking up on volatile organic compounds every time we smell something,” noting that dogs can sense these compounds at much lower levels than humans and that “these compounds are important because they seem to be the key to how dogs are able to smell things like cancer.”

The team worked with five bio-detection dogs that had been trained previously to detect odors associated with conditions such as chronic wasting disease, post-traumatic stress disorder, human ovarian cancer, and human pancreatic cancer. In double-blinded tests, the dogs were presented with blood serum samples from three groups: dogs with confirmed hemangiosarcoma, diseased controls with non-cancerous conditions, and healthy controls. Each dog evaluated 12 matched sample sets across seven trials per set, and none of the samples had been used during their earlier training.

Testing was conducted using olfactometers, devices that, as Wilson describes, “actually have a little infrared laser beam going across the top.” When a dog breaks the beam while examining a sample, the system records that it is interrogating the scent, and if the dog remains in the beam long enough at the correct sample, “they’ll hear a tone, and they’ll know to come and get their treat.” Across all trials, the dogs correctly identified hemangiosarcoma samples 70% of the time, a rate Wilson notes is similar to results seen in studies where dogs detect human cancers. She characterizes the outcome as “very encouraging,” adding that “detecting cancer is incredibly hard—it’s a very complex smell.”

These results show that hemangiosarcoma has a detectable scent profile, which was the central goal of this proof-of-concept study. Wilson suggests that, in the future, a scent-based test might be used as an annual screening tool that could flag potential issues and prompt further diagnostics such as ultrasound or CT scans. Early detection, Otto notes, could “prevent the disease from spreading, because it’s the spread that’s really devastating,” allowing veterinarians to consider removing the spleen before rupture or initiating chemotherapy sooner. Earlier diagnosis would also enable researchers to test additional therapies in clinical trials, a prospect Wilson describes as “an initial kernel of hope.”