Can dogs smell cancer?

The olfactory system of animals has long been useful to humans in several activities, such as hunting, locating people and detecting diseases. Dogs have an acute sense of smell and can sense cancer.

The issue was raised in 1989 when doctors reported the case of a patient concerned about a mole on her thigh that her dog was constantly sniffing and that turned out to be a malignant melanoma. A dog’s nose bears 220 million cells to detect odors compared with only five million cells in humans. Cancers can leave specific traces or odors in a person’s body or its secretions, called odor signatures, which are detectable by man’s best friends, even in very low concentrations.

Researchers have demonstrated that dogs can detect different types of cancer like colorectal, lung, ovarian or breast cancer. Most studies involve dog training to teach them to sniff out specific cancers. For instance, they were able to detect ovarian cancer from blood and prostate cancer from a person’s urine. In 2021, a dog trained to smell breast cancer in urine was shown to be able to distinguish breast cancer patients from a total of 200 people with 100% accuracy.

Canine cancer detection could be used to support the detection and diagnosis of cancer as a non-invasive method. However, further investigations are required to validate its use in real clinical practice.