Feasibility of Integrating Canine Olfaction with Chemical and Microbial Profiling of Urine to Detect Lethal Prostate Cancer

Abstract

Prostate cancer is the second leading cause of cancer death in men in the developed world. A more sensitive and specific detection strategy for lethal prostate cancer beyond serum prostate specific antigen (PSA) population screening is urgently needed. Diagnosis by canine olfaction, using dogs trained to detect cancer by smell, has been shown to be both specific and sensitive. While dogs themselves are impractical as scalable diagnostic sensors, machine olfaction for cancer detection is testable. However, studies bridging the divide between clinical diagnostic techniques, artificial intelligence, and molecular analysis remains difficult due to the significant divide between these disciplines. We tested the clinical feasibility of a cross-disciplinary, integrative approach to early prostate cancer biosensing in urine using trained canine olfaction, volatile organic compound (VOC) analysis by gas chromatography-mass spectroscopy (GC-MS) artificial neural network (ANN)-assisted examination, and microbial profiling in a double-blinded pilot study. Two dogs were trained to detect Gleason 9 prostate cancer in urine collected from biopsy-confirmed patients. Biopsy-negative controls were used to assess canine specificity as prostate cancer biodetectors. Urine samples were simultaneously analyzed for their VOC content in headspace via GC-MS and urinary microbiota content via 16S rDNA Illumina sequencing. In addition, the dogs’ diagnoses were used to train an ANN to detect significant peaks in the GC-MS data. The canine olfaction system was 71% sensitive and between 70-76% specific at detecting Gleason 9 prostate cancer. We have also confirmed VOC differences by GC-MS and microbiota differences by 16S rDNA sequencing between cancer positive and biopsy-negative controls. Furthermore, the trained ANN identified regions of interest in the GC-MS data, informed by the canine diagnoses. Methodology and feasibility are established to inform larger-scale studies using canine olfaction, urinary VOCs, and urinary microbiota profiling to develop machine olfaction diagnostic tools. Scalable multi-disciplinary tools may then be compared to PSA screening for earlier, non-invasive, more specific and sensitive detection of clinically aggressive prostate cancers in urine samples.

Accuracy of a new electronic nose for prostate cancer diagnosis in urine samples

“…have shown that high‐trained dogs recognized PCa‐specific VOCs with a high accuracy 9 . Their findings have been recently confirmed by Guest et al 10 . Unfortunately, today, the routine implementation of dogs in clinical practice presents several limitations, including (i) the need of highly qualified centers, (ii) extensive training for individual dogs and handlers, (iii) the aging profile of dogs and (iv) difficulty to introduce dogs in clinical protocols.…”

“…[6][7][8] In 2015, Taverna et al have shown that high-trained dogs recognized PCaspecific VOCs with a high accuracy. 9 Their findings have been recently confirmed by Guest et al 10 Unfortunately, today, the routine implementation of dogs in clinical practice presents several limitations, including (i) the need of highly qualified centers, (ii) extensive training for individual dogs and handlers, (iii) the aging profile of dogs and (iv) difficulty to introduce dogs in clinical protocols. In addition, US FDA defines with the term "device" "an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including any component, part, or accessory, which is (i) recognized in the official National Formulary, or the United States Pharmacopeia, or any supplement to them, (ii) intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or (iii) intended to affect the structure or any function of the body of man or other animals, and which does not achieve its primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of its primary intended purposes."…”

Diffusion Fails to Make a Stink

“…A robust model describing scent dispersal is of some importance, as olfaction has the potential to be used in the early diagnosis 25 of infections 26 and cancers 27 . In fact, recent work using canine olfaction to train neural networks in the early detection of prostate cancers 28 suggests that future technologies will rely on a better understanding of our sense of smell.…”

Diffusion Fails to Make a Stink

“…A robust model describing scent dispersal is of some importance, as olfaction has the potential to be used in the early diagnosis 25 of infections 26 and cancers 27 . In fact, recent work using canine olfaction to train neural networks in the early detection of prostate cancers 28 suggests that future technologies will rely on a better understanding of our sense of smell.…”