Dogs sniff out bladder cancer

The acute sense of smell that makes dogs useful for detecting illegal substances at airports might also be applied in an oncology setting, researchers reproted this week.

In the British Medical Journal’s September 24 issue, Carolyn Willis, from Amersham Hospital in the UK and colleagues report a proof of principle study showing that dogs can be trained to detect bladder cancer by ‘smelling’ urine.The authors note that tumors produce volatile organic compounds. “Some of these organic compounds are likely to have distinctive odours; even when present in minute quantities, they could be detectable by dogs.”To test this, they used urine samples from 36 patients with bladder cancer and 108 control samples from diseased and healthy individuals; 63 of the samples were used exclusively in final testing of the dogs.The authors trained six dogs of different breeds for 7 months to discriminate between urine from patients with bladder cancer and that of control individuals. Two dogs were trained with dried urine and the remainder with liquid specimens.After training, each dog was offered seven urine samples–one bladder cancer sample and six sex-matched controls. The dogs identified their chosen sample by lying next to it. Each dog underwent the test nine times, and taken together the dogs correctly selected bladder cancer urine on 22 out of 54 occasions, an average success rate of 41% compared to 14% expected by chance alone.”Despite the fact that we had not used dogs with proved scenting abilities, and despite the inclusion of age matched diseased controls, we achieved a statistically significant success rate,” the authors write. “Our study provides the first piece of experimental evidence to show that dogs can detect cancer by olfactory means more successfully than would be expected by chance alone.” “The results we achieved should provide a benchmark against which future studies can be compared, and it is to be hoped that our approach to training may assist others engaged in similar work.”Commenting on the paper, statistician Tim Cole from the Institute of Child Health in London notes that the study was carefully designed. “On balance the results are unambiguous,” he writes in an accompanying commentary. “Dogs can be trained to recognise and flag an unusual smell in the urine of bladder cancer patients.”One control patient seen during the training phase was consistently identified as a cancer case by the dogs, he notes. Although cystoscopy and ultrasound results were negative, the consultant tested the patient again–and found a kidney carcinoma.(Source: BMJ 2004;329:712-714: Reuters Health News: Oncolink: September 2004.)