SAN FRANCISCO—Dogs can be trained to detect prostate cancer by smelling urine samples and signaling the presence of certain volatile organic compounds (VOCs) produced by cancer cells, according to French researchers.

Jean-Nicolas Cornu, MD, of Tenon Hospital in Paris, and colleagues obtained fresh urine samples that had been frozen for preservation from 66 men referred to a urologist because they had an elevated PSA level or abnormal findings on digital rectal examination. Of the 66 men, 33 had prostate cancer and 33 did not, as determined by prostate biopsy.

The dogs used in the study were trained in three phases. In the first phase, which lasted five months, dogs were trained to recognize cancer urine. In the second phase, which lasted 11 months, dogs were trained to discriminate cancer urine from control urine. In the final phase, dogs were presented with five urine samples and prompted to select the one sample that was cancer urine.

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Dogs correctly classified 63 of 66 samples, with three false-positives. The sensitivity and specificity was 100% and 91%, respectively. The positive and negative predictive values were 92% and 100%, respectively.

“These results suggest that VOCs produced by cancer cells can be detected in urine samples,” the authors concluded. “Identification of these substances could lead to a highly specific screening tool for prostate cancer.” Dr. Cornu’s group presented their study findings at the American Urological Association annual meeting.

Previous studies have shown promising results using dogs to detect bladder and breast cancer by smelling urine samples. For example, in a “proof of principle” study by British researchers, trained dogs had a mean success rate of 41% in selecting urine from patients with bladder cancer compared with 14% expected by chance alone, according to a report in the British Medical Journal (2004;329:712-716).