Dogs do as well as state-of-the-art screening tests at sniffing out people with lung or breast cancer. The research raises the possibility that trained dogs could detect cancers even earlier and might some day supplement or even replace mammograms and CT scans in the laboratory.
Two previous studies have shown that dogs seem to be able to sniff out melanomas and bladder cancer. The idea is not outrageous. Cancer patients have been shown to have traces of chemicals – like alkanes and benzene derivatives – in their breath, and other studies have shown dogs can detect chemicals in concentrations as small as a few parts per trillion.
So researchers at the Pine Street Foundation in San Anselmo, California, US, selected three Labrador retrievers and two Portuguese water dogs with no previous training, and over several weeks trained them using breath samples that had been exhaled into tubes by cancer patients.
To test how well the dogs had learned, they used a new batch of samples and had the dogs attempt to distinguish among 55 lung cancer patients, 31 breast cancer patients and 83 healthy controls. The patients had all had their cancers confirmed by biopsy. The tests were double-blind, so neither the dog handlers nor the experimenters knew which tubes were which.
General symptom
The dogs correctly detected 99% of the lung cancer samples, and made a mistake with only 1% of the healthy controls. With breast cancer, they correctly detected 88% of the positive samples, and made a mistake on only 2% of the controls.
The work is convincing, says James C Walker, director of the Florida State University Sensory Research Institute in Tallahassee, US. In 2004 Walker and colleagues showed that dogs could sniff out melanomas. He says that the next step is to see if dogs are really detecting cancer, or if they might be sensing a more general disease symptom, such as one that comes from inflammation.
Walker says he would like, eventually, to see a long, large-scale trial designed to test whether dogs can detect cancer even earlier than standard screening tests.
Journal reference: Integrative Cancer Therapies (vol 5, p 1)
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