Platinum Priority – Prostate CancerEditorial by Anders S. Bjartell on pp. 202–203 of this issueOlfactory Detection of Prostate Cancer by Dogs Sniffing Urine: A Step Forward in Early Diagnosis
Introduction
Prostate cancer (PCa) is the most frequent noncutaneous malignancy in men, with an incidence as high as 192 280 cases per year in the United States [1]. Although prostate-specific antigen (PSA) blood testing remains the most widely used tool for PCa detection [2], important efforts have been conducted to determine alternative biomarkers to overcome its lack of specificity [3]. Novel urine or blood biomarkers have been proposed in the last decade, but none of them is currently widely used [4].
Volatile organic compounds (VOCs) in urine have been proposed as alternative biomarkers [5]. In the case of PCa, it can be postulated that specific VOCs may be present in urine that reveal the presence of a malignant tumor. Basic research has provided a recent finding suggesting that sarcosine could be an indicator of the aggressiveness of prostatic malignant disease [6], but no extensive work searching for VOCs in urine related to the presence of PCa has been published. Promising results about other malignant diseases have been presented [7].
VOC detection can be made by sophisticated biochemical techniques or using animals that have a highly sensitive sense of smell [7]. Some previous work suggested that dogs trained to smell urine could recognize lung, bladder, or breast cancer with various success rates, but no positive results have been published concerning PCa [8], [9]. To determine if some VOCs in urine could result in a specific odor associated with PCa, we specially trained a dog and conducted a double-blind study to check its ability to detect PCa by sniffing urine.
Section snippets
Dog training
A Belgian Malinois shepherd was trained by a professional and dedicated team of two people from the beginning to the end of the study. The dog belonged to the French Army veterinary department and was chosen among young dogs destined for explosives detection training. The dog was never trained before.
The first objective was to teach the dog to discriminate between urine from individuals with PCa and urine from controls. The dog was trained by the clicker training method (a kind of operant
Results
Characteristics of patients who supplied urine for the testing phase are given in Table 1. Thirty-three runs were conducted during the double-blind testing phase. The mean duration of each run was approximately 30 s. In 30 cases, the dog sat in front of the cancer sample. In three runs, the dog sat in front of a control sample. In these three cases, the control samples incorrectly classified were considered false positives, and the three cancer cases were considered false negatives.
Discussion
The use of canines for cancer detection emerged after the first case report in 1989 about a melanoma detected by a dog on his owner’s leg [10]. The scientific basis of this ability of dogs to detect the odor signature of cancer is believed to be linked to the VOCs produced by malignant cells [5]. Indeed, basic research studies have established that during tumor growth, protein changes in malignant cells lead to peroxidation of the cell membrane components and produce VOCs that can be detected
Conclusions
The present study brings the proof that a specially trained dog by a professional team can be conditioned to recognize PCa among controls only by sniffing urine. This study opens the door of VOC detection for PCa diagnosis. Metabolomic studies should complete this approach by determining the volatile molecular signature of PCa.
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