The Nose Knows, It Seems

Some years ago there was a report of a dog that was able to detect melanoma by repeatedly sniffing at a lesion. This inspired a group of Californian acupuncturists to try an experiment on a larger scale. They borrowed 5 dogs from the Guide Dogs for the Blind (3 Labs and 2 Portuguese water dogs). The dogs were trained to distinguish between exhaled breath samples from 55 lung cancer patients, 31 breast cancer patients, and 83 healthy controls, using a simple food reward system. The cancer patients represented all 4 different stages of their cancer type.

After training, the dogs were able to detect the lung cancer samples with 99% accuracy (sensitivity). For breast cancer, the accuracy was slightly less (88%) but still impressive. (I will discuss the difference between the ‘sensitivity’ and specificity’ of tests at another time.) The results were quite similar for all 5 dogs used, suggesting that many different dogs might be used for this sort of training.

How can dogs be so good at this? It’s their exquisitely sensitive noses, capable of detecting scent molecules in the parts-per-trillion range; this is better than the ability of the most sensitive instrument: gas chromatography/mass spectrometry (GCMS). Some liken it to the ability to detect a specific grain of sand on the beach.

This report, which is posted online at the Integrative Cancer Therapies journal website, gives sufficient details of the method for dog trainers (and oncologists) to be able to assess its potential usefulness. It provides another instance of beneficial interactions between and man and his best friend.