Sniffing out PCa – from dogs to the eNose

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It is always humbling to see how much you can miss in trying to keep up with medicine’s developments, even in an incredibly narrow area like prostate cancer. Fortunately, there are many crutches like Medscape that offer help (along with targeted ads of course). Reading through their recent post on the top stories in medicine in 2014, I was chagrined to learn that Medscape readers listed the eNose for detecting prostate cancer as the 3rd most innovative advance in 2014. Really?? I hadn’t heard a single presentation or comment on this at any of the cancer meetings I faithfully attend to keep up. Well, time to write a brief post, even if all of you didn’t bring this to my attention either!

The article in question appeared in July in the Journal of Urology. Researchers in Finland (my “second country”, having spent a delightful year on sabbatical there in the 1980’s – and no, I don’t speak the language…) utilized the “ChemPro® 100-eNose” to sniff the air over urine samples from men with BPH vs prostate cancer, and then determine whether the chemicals in that air could discriminate between the benign vs malignant condition. Although the study was very small, (50 prostate cancer patients compared to 15 BPH patients), “the eNose reached a sensitivity of 78%, a specificity of 67% and AUC 0.77” according to the abstract.

There is a substantial literature on the ability of trained dogs to detect cancer in humans by sniffing either their exhaled breath or urine. In one review, reported sensitivity and specificity can be close to 100% for lung cancer. However, as with any system that relies on an animal focusing on a difficult task, there seems to be a wide range of issues regarding reproducibility. A good example of how this research goes is an attempt to detect bladder cancer by training dogs to sniff the urine of patients vs controls. Accuracy was clearly better than chance alone (41% vs 14% expected by chance alone), but far below what we need to adopt a procedure for routine use in medicine. For prostate cancer, the Europeans seem to be taking the lead in attempting to improve on the technology – in one case, using a single trained “Belgian Malinois shepherd”!

The eNose used in the Finnish study is an example of ongoing attempts to replace the dog by using electronic detectors to sample volatile chemicals in air. In their study, a thin layer of urine was pipetted into a plastic petri dish to allow evaporation of the chemicals, and the resultant gas was ported to the machine which is described in the article as follows: “The eNose used in this study is a commercially available model (ChemPro® 100, Environics Inc., Mikkeli, Finland) based on the ion mobility spectrometry principle. The device contains an ion mobility cell that consists of 8 electrode strips producing 2-channel output and a metal oxide based semiconductor cell. Together these sensors produce 18-channel measurement data. The sensors do not specify molecules but produce a characteristic smell print of the sample.” In accompanying editorials, there are concerns raised regarding the methodologies, how applicable this might be in the “real world”, and so forth, but in lung cancer there is even some evidence that different stages and types of lung cancer can be detected using this sort of technology. The holy grail in prostate cancer detection remains finding a way to non-invasively discriminate the “lethal phenotype” that needs treatment from the “background” of the >80% of men who will develop prostate cancer that will never bother them by the time they reach age 90. Perhaps this technology will evolve to contribute to that goal.

4 Comments

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4 responses to “Sniffing out PCa – from dogs to the eNose

  1. Bob Lederer

    Interesting. I read it in July but when no one else, including you commented, I passed on it thinking it was not important. Still hoping for that magic test that discriminates. I would let any dog sniff anything he wants! Happy New Year.

  2. If the histopathology alone can’t tell for certain, I’d forget the noses for now.
    Happy New Year, sport.

  3. Are there alternative animals with even keener olfactory divination than that of canines?

    • Good question. Of course you can google anything these days which brought me to this article and the following paragraph:
      Scenthounds as a group can smell one- to ten-million times more acutely than a human, and Bloodhounds, which have the keenest sense of smell of any dogs,[citation needed] have noses ten- to one-hundred-million times more sensitive than a human’s. They were bred for the specific purpose of tracking humans, and can detect a scent trail a few days old. The second-most-sensitive nose is possessed by the Basset Hound, which was bred to track and hunt rabbits and other small animals.

      Bears, such as the Silvertip Grizzly found in parts of North America, have a sense of smell seven times stronger than that of the bloodhound, essential for locating food underground. Using their elongated claws, bears dig deep trenches in search of burrowing animals and nests as well as roots, bulbs, and insects. Bears can detect the scent of food from up to 18 miles away; because of their immense size, they often scavenge new kills, driving away the predators (including packs of wolves and human hunters) in the process.

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