Dogs sniffing urine: a future diagnostic tool or a way to identify new prostate cancer markers?

There is a need to develop screening methods for early detection of cancer of all kinds. Although mammography and prostate-specific antigen (PSA) screening have been described as reducing mortality rates in breast and prostate cancer (PCa) [1,2], we need more specific and sensitive methods for cancer diagnostics. The low specificity of the PSA test in PCa detection has been a subject of discussion over the last decade [3]. Volatile organic compounds (VOCs) are chemical compounds (mainly the products of cell catabolism) found as gases in human breath but also detected in urine. Basic research studies have shown that changes in malignant cells during tumor progression lead to peroxidation of cell membrane components and subsequent release of VOCs [4]. Different methods have been developed to analyze VOCs. In 2007, Belda-Iniesta and collaborators reviewed the literature regarding studies comparing lung cancer patients with healthy controls and concluded that promising results were obtained [5]. Recent reports point in the same direction [6]. The idea of using dogs for cancer-screening purposes by sniffing VOCs in exhaled breath or urine is excellent; however, only a few studies are published on this topic. In 1989, a case of malignant melanoma was detected by a dog sniffing his owner’s leg [7]. Later studies have shown that trained dogs were able to detect bladder, lung, or breast cancer by sniffing urine [8], but failures were reported in PCa patients [9]. In this issue of European Urology, Cornu et al. [10] report the first successful results using a dog in PCa detection. A Belgian Malinois shepherd was trained by a professional and dedicated team over 24 mo including a learning phase and a training period. The dog was trained to recognize in a