Sniffing Out Bladder Cancer

November 10, 2004

Dogs may help doctors detect bladder cancer! A new study published in the British Medical Journal shows that dogs can be trained to identify urine samples from people with bladder cancer.

Dr. Carolyn Willis and her colleagues from the Department of Dermatology at Amersham Hospital (Amersham, UK) trained six dogs over seven months to discriminate between the urine from people with bladder cancer from that of people without bladder cancer. The dogs were presented with seven samples: only one of the seven samples was from a person with bladder cancer. Therefore, if the dog randomly selected a sample, the chance of finding the bladder cancer sample was only 1 in 7 (~14.3%).

The investigators were careful to avoid giving the dogs clues about the samples. For example, the samples were presented to the dogs by a researcher who did not know which dish had the cancer sample.

Each of the six dogs was tested nine times for a total of 54 trials. As a group, the dogs correctly identified the bladder cancer samples in 22 of the 54 trials (41%). This is much better than the random chance detection rate (14.3%).

The scientists are unsure how the dogs detect the bladder cancer samples. They think that bladder cancer may cause specific chemicals to be released into urine. Dogs may be able to use their sensitive sense of smell to identify these chemicals in the samples.

The researchers also mentioned that all of the dogs alerted to one urine sample from one person in the control group. This person had normal laboratory tests and had not been diagnosed with bladder cancer. An investigator was concerned about this finding and requested further laboratory tests. After further tests, this person was found to have cancer of the kidney!

Certainly, further research about how dogs can detect disease needs to be conducted. Although dogs were able to detect bladder cancer samples at a rate better than chance, they still found less than 50% of the diseased samples. Perhaps with further training, dogs will some day work with doctors to help diagnose disease.

Reference and further information:

  1. Willis, C.M., Church, S.M., Guest, C.M., Cook, W.A., McCarthy, N., Bransbury, A.J., Church, M.R. and Church, J.C. Olfactory detection of human bladder cancer by dogs: proof of principle study. British Medical Journal, 392:712-714, 2004.
  2. Bloodhounds: King of the Trackers - from Neuroscience for Kids
  3. The Nose Knows - from Neuroscience for Kids
  4. Our Chemical Senses: Olfaction - from Neuroscience for Kids
  5. Police Dogs - Theory of Scent
  6. Suspect Identification by Scent

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